OF TH E; SWEE T ?EA 

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COPYRIGHT DEPOSIT. 



OTHER WORKS 
BY THE SAME AUTHOR 



Diseases of Truck Crops and their Control 
[In Preparation] 

Diseases of Greenhouse Plants 
[In Preparation] 

Diseases of the Sweet Potato 
[In Preparation] 



E. P. DUTTON & CO 

NEW YORK 







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THE CULTURE AND DISEASES 
OF THE SWEET PEA 



BY 

J. J. TAUBENHAUS, Ph.D. 

Plant Pathologist and Physiologist in Charge. Experiment 
Station, Agricultural and Mechanical College of Texas 



NEW YORK 

E. P. DUTTON & COMPANY 

681 FIFTH AVENUE 



S:&4I3 
•SlTs 



Copyright, 1917 
By E. P. DUTTON & COMPANY 



PRINTED IN THE UNITED STATES OF AMERICA 
I 



MAY 3! 1917 

©CI.A467396 



TO 

The REVEREND CHAIM HIRCHENSOHN 

WITH LOVE AND DEEP AFFECTION 



PREFATORY NOTE 

The keen appreciation of the public of 
the beauties of nature as expressed in the 
building of parks and public gardens, in 
the planting of street trees, and in the 
adornment of private grounds and homes 
by means of ornamental plants is one of 
the most distinctive marks of an advanced 
civilization. The success of these under- 
takings means the overcoming of many 
difficulties which the casual observer fails 
to appreciate. It means not only the se- 
lection and arrangement of varieties in 
such manner as to meet with the most 
aesthetical tastes of the public, but it fre- 
quently means growing the plants under 
new environmental conditions, the study 
of soil and climate, the contest against 
insects and diseases which continually 

threaten the existence of these plantings. 

vii 



viii PREFATORY NOTE 

It has long been known that unfavor- 
able soil and climatic conditions and de- 
structive insects were very important fac- 
tors in plant culture, but it is only within 
recent years that the public has begun to 
appreciate that many of the difficulties in 
growing plants, in fact, many of the fail- 
ures are due to diseases. Most of these 
diseases are due to fungus or to bacterial 
organisms. Since most of these organisms 
are so small that they cannot be seen ex- 
cept with the aid of a microscope, the 
grower has usually attributed the disease 
to other causes. The appreciation of these 
facts makes a work on the growing of any 
group of ornamental plants in which the 
importance of the control of the diseases 
is given a prominent place very desirable. 
Therefore, this work on the Growing of 
Sweet Peas, by a worker who has made a 
special study of the diseases is very timely. 



PREFATORY NOTE ix 

The sweet pea is a favorite flower with 
the great majority of people. It is en- 
joyed by both the high and the lowly, and 
is within the reach of all. It is a profuse 
bloomer and presents an untiring variety 
of sizes and delicate colors. It is well 
adapted to various conditions and can be 
grown over a very large part of the world. 

The author's training in plant pathology 
and his large experience with diseases of 
ornamentals is a guarantee of meritorious 
character of the work. The work is both 
practical and scientific; it is equally use- 
ful to the layman, the commercial grower 
and to the scientist; it deals not only with 
the diseases of sweet peas, but with the 
cultivation and other important questions 
connected therewith. 

MEL. T. COOK. 
Rutgers College, 

New Brunswick, N. J. 
January, 1917. 



PREFACE 

The sweet pea is unfortunately one of 
those crops which has received scant con- 
sideration in horticultural text books. 
The field to be covered by the latter is so 
large that their treatment of many a crop 
is necessarily meager. Good articles on 
the culture of the sweet pea are to be found 
in various journals, but are not accessible 
to the practical grower. The cultural di- 
rections which seed concerns publish for 
the benefit of their patrons are brief; and 
Mr. Harrison Dick's "Sweet Peas for 
Profit" covers only one phase of the sub- 
ject, namely, the greenhouse culture. As 
no complete study of the sweet pea has 
been published in America, it is felt that 

this book may be very timely, especially 

xi 



xii PREFACE 

since this delicate flower is gaining so rap- 
idly in popularity. 

The chief difficulty encountered by the 
growers of the sweet pea is the combating 
of diseases, in which they have had very 
little help. Massee and Chittenden in 
England have devoted some time to the 
"Streak disease," but these workers have 
been misled in their observations by at- 
tributing this disease to the fungus Thie- 
lavia. In the United States, floral pathol- 
ogy is still in its embryonic stage, and the 
sweet pea was not the first to claim the at- 
tention of Pathologists. The author of 
this book in the last three years has pub- 
lished several papers on his own investi- 
gations, taken up largely because of nu- 
merous complaints from growers who met 
with failure in their attempts to grow this 
beautiful flower. Florists and gardeners 
have often been hopelessly discouraged 



PREFACE xiii 

the first time they tried to grow sweet peas 
because of total loss from disease. Others 
who have grown them for years have been 
meeting with difficulties that are consider- 
ably reducing their profits. The layman, 
particularly the housewife so proud of her 
row of sweet peas by the house, has seen 
many of them carried off by blights and 
the remainder dry up and wither away. 

Naturally the blame fell at once on the 
seedsman, who was accused of supplying 
a poor grade of seed. In seeking justifica- 
tion, seedsmen attributed the growers' 
failures to bad weather, to drought, or to 
the green aphids. A few seed catalogues 
and some popular articles on the culture 
of the sweet pea asserted that the plant is 
unusually free from disease, and that all 
failures are due to overfeeding. Many 
practical men do not realize that plants 
have diseases just as do animals and hu- 



xiv PREFACE 

man beings. We shall here endeavor to 
show that although bad weather, over- 
feeding, etc., may be important factors, 
they are not the fundamental reasons for 
failure. We shall study the specific causes 
that lead to the diseases of the sweet pea; 
the definite parasitic forms of life such 
as insects, fungi, and bacteria that live 
upon this plant and bring about its de- 
struction. The nature of the attacking 
insects is still incompletely known and 
there is urgent need of further investiga- 
tion of them. Of the fungi, nine produce 
serious diseases in either roots, stems, foli- 
age, or blossoms of sweet peas. Only one 
bacterial trouble, however, is so far known 
to affect sweet peas, and that is the dreaded 
"Streak." To these troubles may be added 
eel worm, red spider, and mites, all of 
which add considerably to the losses. 
In the discussion which is to follow, 



PREFACE xv 

technical terms as far as possible will be 
avoided, with the exception, however, of 
the scientific names of the parasites. Pop- 
ular terminology does not always distin- 
guish between diseases of different nature 
that are apparently alike. For example, 
the term "blight" is applied to diseases of 
similar symptoms but of quite different 
causes. Methods of controlling a disease 
are directly dependent on a knowledge of 
the nature and cause of the particular 
trouble. Taking insect pests as an exam- 
ple, it is essential to know whether they 
are biting or sucking, each class requiring 
different treatments. 

The writer feels that no apology is 
needed for allowing space in this book to 
a discussion of the culture of the sweet 
pea. No matter from what angle we look 
at it, we cannot deny the fact that plant 
diseases are directly dependent on the cul- 



xvi PREFACE 

tural conditions of the host. In other 
words, the attack of most plant diseases 
depends on some weak point in the cul- 
tural methods which has weakened the 
host at some phase in its life history. If 
we accept the definition of disease as any 
serious deviation from the normal; and 
admitting as we do that proper cultural 
conditions are necessary to maintain the 
proper balance of health of a plant, it be- 
comes self evident that a discussion of 
culture requirements goes hand in hand 
with any discussion on plant diseases. To 
be more specific, it is very apparent that 
the man who understands plant life in all 
its aspects will be in a much better posi- 
tion to also cope intelligently with any 
problem of disease which may confront 
him at any time. Since growers as a rule 
must be their owri plant doctors they can- 
not be provided with too much informa- 



PREFACE xvii 

tion on cultural requirements of the par- 
ticular crop with which they are concerned. 

Although the writer had considerable 
experience in growing sweet peas in the 
open and in the greenhouse, he felt that 
this ground could be so much better cov- 
ered by eminent specialists such as Pro- 
fessor Beal of Cornell University; Mr. 
Cuthbertson, Messrs. Morse and Co., and 
all the others who are here quoted. 

It may perhaps be the opinion of a few 
that a book on plant pathology should not 
include a discussion on insect pests. The 
writer, however, believes that in a specific 
work of this nature such a discussion is in- 
valuable. Insects are known to be car- 
riers of numerous plant diseases. In this 
work it would be rather difficult to give a 
complete discussion of Mosaic, or in fact 
of any of the other sweet pea diseases if 
we were to leave out of consideration the 



xviii PREFACE 

damage caused by the Pea Aphis, or any 
other of the insect pests here described. 
The writer did not trust to his own knowl- 
edge of Entomology. Insect specimens in 
each case were submitted to the Depart- 
ment of Entomology, United States De- 
partment of Agriculture for identification, 
and there due credit belongs. 

This book is primarily intended to be a 
practical treatise. The aim cannot be at- 
tained if our study is to be deprived of its 
scientific basis and its scientific value. It 
is hoped this double character of the work 
will make it a means of ready reference 
for both growers and investigators. 

During the past four years numerous 
letters of inquiry have been received by 
the writer from sweet pea growers rela- 
tive to various difficulties, especially those 
of a pathological nature. Although hesi- 
tating to make hasty suggestions, we could 



PREFACE xix 

not turn a deaf ear to the numerous re- 
quests from sweet pea growers as well as 
from technical men who urged the prepara- 
tion of a book of this nature. The writer 
seriously solicits suggestions or criticism 
of this work. 

Acknowledgments are due to Professor 
A. C. Beal, Mr. F. G. Cuthbertson, and 
C. C. Morse and Co. for valuable contri- 
butions on the culture of the sweet pea. 
To Mrs. D. de Sola Pool (nee Miss Tamar 
Hirchensohn), previously of the Faculty 
of Hunter College, N. Y.; to Dr. Owen 
Sypherd of Delaware College, to Dr. C. 
H. Farr of the A. and M. College of 
Texas, to Dr. M. T. Cook of Rutgers 
College for suggestions in reading the 
manuscript. To the Delaware Experi- 
ment Station for figs. 7 to 21, 25 to 31, 38, 
42, 43, and 45, all of which were origin- 
ally taken by the author. All the other 



xx PREFACE 

figures have been accredited in their proper 
places. 

Last but not least, acknowledgment is 
due my wife, Esther Michla Taubenhaus, 
by whose inspiration this work was made 
possible. 

J. J. Taubenhaus. 
College Station, Texas. 



CONTENTS 

PAGE 

Introduction l 

CHAPTER 

I History, Evolution, Classification and 

Culture 9 

II Culture of the Sweet Pea for Seeds . 60 

III Culture of Sweet Peas Under Glass . 74 

IV Diseases of Greenhouse Sweet Peas . . 90 
V Field Diseases of Sweet Peas . . . .135 

VI Diseases Not Yet Known in America . 149 

VII Insect Pests 152 

VIII Diseased Seeds 176 

IX Physiological Diseases 181 

X Methods of Control 185 

XI Spraying 204 

Index 227 



ILLUSTRATIONS 

A Fine House of Sweet Peas . . . Frontispiece 

HO. PAGE 

1 Method of Growing Sweet Peas from Seed in 

England 39 

2 Trial Grounds of C. C. Morse & Co. . . . 70 

3 Field of Morse's White Spencer .... 70 

4 Sweet Peas and Carnations 89 

5 Root Rot caused by Rhizoctonia . 99 

6 Root Rot caused by Rhizoctonia .... 99 

7 Hyphae of Rhizoctonia 102 

8 Culture of Sweet Pea Rhizoctonia . . . .102 

9 Culture of Fusarium Lathy ri 102 

10 Chaetomium Spirochaete 107 

11 Fusarium Wilt 110 

12 Root Rot caused by Thielavia 113 

13 Root Rot caused by Thielavia 114 

14 Mycelium of Thielavia 116 

15 Powdery Mildew 119 

16 Sclerotia of the Sweet Pea Sclerotinia . . .119 

17 Sclerotinia Wilt in Seedlings 120 

18 Root Knot in Sweet Peas 124 

19 True Legume Root-Nodules 124 

20 Greenhouse Thrips 131 

21 Red Spider 132 

22 Triphleps Insidiosus 133 

23 Anthracnose Disease on the Stem . . . .138 



ILLUSTRATIONS 

PIG. PAGE 

24 Anthracnose Disease on the Leaf . . . .138 

25 Bitter Rot of Apple 141 

26 Sweet Pea Mosaic 141 

27 Dwarfing of Plant due to Mosaic . . . .142 

28 Plant Outgrowing Mosaic 144 

29 Culture of the Streak Organism .... 148 

30 Sweet Pea Aphis Parasitized 148 

31 Sweet Pea Aphis 153 

32 How Aphids Feed 156 

33 The Convergent Lady Beetle 159 

34 Syrphid Fly 160 

35 Green Lace Fly 162 

36 Aphidius Testaceipes Ovipositing . . . .163 

37 Aphelinus Nigritus 166 

38 The Striped Blister Beetle 170 

39 Variegated Cut Worm 171 

40 White Grub (May Beetle) 174 

41 Anthracnose Disease on Pods 177 

42 Fusarium and Botrytis Fungi 178 

43 Auto-spray No. One 180 

44 The Drugstore Beetle 180 

45 Soil Infected with Fusarium Lathy ri . . .191 

46 Spraying the Sweet Pea Field 2 18 



CULTURE OF THE 
SWEET PEA 

INTRODUCTION 

The ancients believed that diseases in 
plants were induced by evil spirits. For 
instance, the rust of wheat was thought by 
the Romans to be caused by the evil spirit 
Rubigo. The remedy then employed was 
to frighten away the spirit by beating with 
drums of various kinds. To-day, some 
insist that all plant diseases are brought 
about by conditions of environment such 
as excessive sunshine, drought, rain or 
dew. We may perhaps justify these views 
when we consider that plants in their mute 
way are unable to tell of their ailments. 
The keen eye and the close observer, how- 



2 CULTURE OF THE SWEET PEA 

ever, have singled out on plants parasitic 
organisms whose work brings about devi- 
ations from the normal. To-day Plant 
Pathology has become recognized as a 
definite science. There is hence no reason 
why we should tolerate certain plant dis- 
eases when we realize the vast store of 
scientific knowledge available. Indeed it 
is highly imperative that any man who is 
engaged in the growing of crops should be 
able to recognize a diseased condition in 
plants. 

Like every science, Plant Pathology has 
made slow progress in its beginning. 
Scholars who considered it from a purely 
speculative or philosophical point of view 
only were interested in it at first. It was 
really during the first half of the nine- 
teenth century that Plant Pathology built 
for itself a solid foundation, and gained 
a place among the leading sciences. It 



INTRODUCTION 3 

seems that it was very difficult for schol- 
ars previous to the nineteenth century to 
believe otherwise but that parasitic fungi 
were emanations or waste products of the 
higher plants. It was DeBary who first 
established definitely that healthy plants 
may be attacked and penetrated by fungi. 
This important discovery has forever dis- 
pelled doubt as to the parasitic nature of 
most plant diseases. Nevertheless, the 
economic aspect of Plant Pathology could 
not gain much impetus as long as growers 
were content to lose annually from five to 
forty per cent, of their crops. It required 
severe epidemics to arouse the attention of 
farmers in which cases they turned to the 
scientist for help. An instance of this is 
the epidemic of late blight of potatoes in 
Ireland, in 1845, which practically re- 
sulted in famine and great hardship to the 
people. Unfortunately, there were no 



4 CULTURE OF THE SWEET PEA 

trained Pathologists at that time to cope 
with the situation. A similar epidemic 
was that of downy mildew of grapes in 
France, in 1882. France, however, met 
the crisis through one of her noble sons, 
Professor M. Millardet, then of the Acad- 
emy of Science at Bordeaux. His keen 
observations and studies have evolved a 
remedy for the grape mildew. Millardet 
was in fact the first to show the value of 
copper as a fungicide; and incidentally 
also laid the foundation to modern meth- 
ods of spraying and of disease prevention 
in general. To-day Plant Pathologists 
are everywhere investigating plant dis- 
eases which cause serious epidemics. And 
they are going farther, for the diseases of 
every weed is important and will aid in 
the solution of many problems regarding 
disease in vegetables, fruits and crops. 
Although nearly every Agricultural Col- 



INTRODUCTION 5 

lege or University in the United States 
offers courses in Plant Pathology, the sup- 
ply of trained investigators is neverthe- 
less limited. Since every Experiment Sta- 
tion is directly supported by state and 
federal funds, it is natural that every 
worker is more or less impelled to inves- 
tigate diseases of plants which are of 
greatest economic importance. For this 
reason nearly all the research was directed 
to fruit, cereal and forage crops. Flower 
pathology is as yet in its embryonic stage. 
To-day there are but few institutions of 
learning which have established definite 
divisions in the investigation of diseases 
of ornamental plants. As stated in the 
preface, the sweet pea diseases have 
received scant attention, except those 
worked by the writer. Even in this case 
for lack of funds the investigations were 
brought to an untimely end. The little 



6 CULTURE OF THE SWEET PEA 

that the writer was able to contribute was 
made possible through the moral sup- 
port of the American Sweet Pea Society; 
and especially by money donations from 
the various seedsmen and other lovers of 
the sweet pea in the United States. 

It is believed that the present work is 
fulfilling an urgent need. There never 
was a time when ornamental plants were 
grown commercially on a larger scale than 
to-day. In fact the sweet pea itself forms 
an industry, the economic importance of 
which cannot be overlooked. It is within 
recent memory of all when the hollyhock 
occupied the place of honor in every gar- 
den. In every flower exhibit in this coun- 
try or abroad it was king. To-day the 
hollyhock is only mentioned as ancient his- 
tory. Diseases have so crippled that beau- 
tiful plant, that growers out of sheer dis- 
couragement have ceased raising it. Now 



INTRODUCTION 7 

it is found occasionally near abandoned 
houses or in neglected back yards. The 
sweet pea is undergoing similar critical 
periods. In England, for instance, the 
"Streak" already constitutes a serious 
menace to profitable sweet pea culture. 
The same conditions are beginning to pre- 
vail in the United States, and several per- 
plexing diseases now threaten the eco- 
nomic existence of one of the most delicate 
of flowers. 



CHAPTER I 

HISTORY, EVOLUTION, CLASSIFICATION AND 
CULTURE * 

Among the annual flowers none excel 
the sweet pea in beauty, usefulness, fra- 
grance, and range of color. No annual 
flower is more popular. If the rose is the 
Queen of Flowers, the sweet pea is a truly 
royal princess worthy of her train. This 
flower has long been grown in England 
and America; of late years it has been 
gaining in favor in continental Europe; 
and it is also extensively grown in far-off 
Australia and Tasmania. 

The sweet pea is a native of the island 
of Sicily. It was first mentioned in 1695 

1 By Professor A. C. Beal of Cornell University. 
9 



io CULTURE OF THE SWEET PEA 

by an Italian monk who sent seeds to Eng- 
land and Holland. In England sweet 
peas were cultivated in many gardens. 
The plant is one of the species of Lathy- 
rus, which is a genus of Leguminosae. Un- 
like other species of this genus, the sweet 
pea has fragrance, and Linnseus gave it the 
name of odoratus. Its scientific name, 
therefore, is Lathyrus odoratus. The 
color of the original sweet pea was purple 
in the standard, and sky-blue in the wings. 
During the first one hundred years of 
its history there was little improvement 
in the sweet pea. A variety with white 
flowers and another with pink and white 
flowers were developed. The first half of 
its second century of cultivation was sig- 
nalized by the development of several va- 
rieties, so that in i860 there were nine 
known varieties. About this time seeds- 
men began to take greater interest in 



HISTORY AND EVOLUTION n 

sweet peas; but more varieties came in 
slowly. Every flower, however, that has 
won popular favor has had at least one 
great genius to develop it. The greatest 
genius in sweet peas was Henry Eckford, 
who commenced crossing the best obtain- 
able varieties about 1878, and began to 
sell new varieties in 1883. Steadily he 
kept at work until, at his death in 1905, 
although the number had increased to 
more than three hundred, he was to be 
credited with originating most of the lead- 
ing varieties. About 1890, the American 
sweet pea growers began to appreciate the 
beautiful varieties Mr. Eckford was send- 
ing out and there was a wave of popularity 
for the flower. The discovery that Cali- 
fornia had a favorable climate for the pro- 
duction of sweet pea seed enabled the 
seedsmen to supply the greatly increased 
demand. This development has con- 



12 CULTURE OF THE SWEET PEA 

tinued until the larger part of the world's 
supply now comes from California. 

Meanwhile the variety Blanche Ferry 
was discovered growing in a garden in 
New York State and was put on the mar- 
ket in 1889. From this was developed the 
varieties Early Blanche Ferry, Earliest of 
All, Earliest White, and the whole race of 
winter-flowering sweet peas. The Ameri- 
can originators have given us many good 
striped varieties, such as America, Aurora, 
etc., and also such blues as Navy Blue and 
Flora Norton. Other notable varieties 
are Helen Pierce, Dainty, Janet Scott, 
Emily Henderson, Phenomenal, Stella 
Morse, Admiration, Shasta, and White 
Wonder. The dwarf or Cupid sweet peas 
originated in California and were offered 
in 1896. 

During the closing years of Mr. Eck- 
ford's busy life, at a time when some grow- 



HISTORY AND EVOLUTION 13 

ers thought that the limit of development 
in sweet peas had almost been reached, a 
new type of sweet peas appeared. This 
was the waved or Spencer type. The first 
variety, Countess Spencer, sent out by Mr. 
Cole (the originator) in 1904, was at once 
very popular, and since that time there 
has been an extraordinary interest in sweet 
peas on both sides of the Atlantic. How- 
ever, the greatest interest has been in Eng- 
land, where a great many persons are in- 
terested in originating new varieties and 
a large number are placed on the market 
each year. Numerous exhibitions are 
held, and the National Sweet Pea Society 
has over one thousand members. 

Although the interest in sweet peas in 
America is not so intense, yet this flower 
is seen in almost every home garden, 
where it is cherished for its special 
beauty. 



14 CULTURE OF THE SWEET PEA 

The sweet pea may be classified accord- 
ing to the habit of the plant into 

^,. ,. [Garden varieties 
Climbing :-L- r n 

[ W lnter-nowenng 

-p. r [Cupids 

[Bush varieties (now obsolete) 
It is important to remember that the win- 
ter-flowering varieties are absolutely dis- 
tinct from the garden varieties in their 
habit of growth. The Cupids are occa- 
sionally grown because of their novelty. 

Sweet peas are usually classified accord- 
ing to the form of the flower. The earliest 
known varieties of the sweet pea had flow- 
ers in which the standards were reflexed 
and deeply notched at the apex. The ef- 
fort of Mr. Eckford and others was to 
eliminate the notch and give the standard 
greater substance so that it could hold it- 
self erect. This brought about the open 
form which often retained something of 



HISTORY AND EVOLUTION 15 

the apical notch. Then came the hooded 
form, in which the edges of the standards 
are rolled forward. There are various de- 
grees of hooding in different varieties. 
Extreme hoodings were at one time recog- 
nized under the name of snapdragon va- 
rieties, which were never more than a pass- 
ing novelty. Finally, there is the waved 
form in which the edges of the standards 
and often the wings are beautifully 
waved. This is the most handsome form 
of sweet pea flower (the flowers are larger 
and have longer stems) , and it is probable 
that the other forms will pass away. The 
older types, however, seed more freely, and 
therefore it has been possible to produce 
seed more cheaply. However, any one 
who has grown the waved or Spencer va- 
rieties will not again take up the culture of 
the old varieties, and therefore in the 
course of time the latter are doomed. 



i6 CULTURE OF THE SWEET PEA 

The following is a classification of 
sweet peas according to form : 

Garden type Winter- flowering Dwarf Type 

type (Cupid) 

Open form Open form Open form 

Hooded form Hooded form Hooded form 
Waved form Waved form 

Sweet peas are classified also according 
to color. The English Sweet Pea Society 
recognizes thirty-two color classes as fol- 
lows: Bicolor; Blue; Blush; Carmine; 
Cerise; Cream, Buff, and Ivory; Cream- 
pink (Pale) ; Cream-pink (Deep) ; Crim- 
son; Fancy; Lavender; Lilac; Magenta; 
Marbled and Watered; Maroon; Maroon 
Purple; Maroon Red; Mauve (Dark) ; 
Mauve (Pale) ; Orange-pink; Orange 
Scarlet; Picotee Edged (Cream Ground) ; 
Picotee Edged (White Ground) ; Pink 
(Deep) ; Pink (Pale) ; Rose; Salmon 
Shades; Scarlet; Striped and Flaked 



HISTORY AND EVOLUTION 17 

(Purple and Blue) ; Striped and Flaked 
(Chocolate on Gray Ground) ; Striped and 
Flaked (Red and Rose) ; White. 

When one compares this with the fol- 
lowing classification used in a prominent 
seedsman's catalogue only fifteen years 
ago, one can appreciate the marvelous de- 
velopment in the sweet pea. This cata- 
logue grouped all varieties under White, 
Cream, Light Yellow, Light Blush, 
Light Pink, Deep Pink, Rose, Red and 
Scarlet, Shades of Orange and Salmon, 
Pink and White, Blue and White, Claret 
and Maroon, Striped and Variegated, 
Lavender and Light Blue, and Blue and 
Purple. 

Varieties 

Catalogues usually classify sweet peas 
according to color with a separate list of 
the winter-flowering varieties. 

More than twelve hundred varieties 



18 CULTURE OF THE SWEET PEA 

of sweet peas have been introduced. 
Many varieties have passed into oblivion, 
but there are large numbers in the 
trade and every season witnesses a con- 
siderable number of aspirants for public 
favor. The following list is the result of 
testing hundreds of varieties during the 
last few years. It is a matter of personal 
taste whether some of the colors, as repre- 
sented by the color sections, are desirable 
for any particular garden. The classifica- 
tion will enable any one to select those col- 
ors and varieties suited to individual 
tastes. 

WAVED VARIETIES 

Bicolor — Mrs. Cuthbertson, Colleen 

Blue — Margaret Madison, Flora Norton Spencer, 

Blue Jacket 
Blush — Lady Evelyn Eyre, Princess Victoria, 

Florence Morse Spencer 
Carmine — John Ingman 
Cerise — Chrissie Unwin 



HISTORY AND EVOLUTION 19 

Cream, Buff, and Ivory — Primrose Spencer, Isabel 
Malcolm, Primrose Beauty, Lady Knox, 
Queen Victoria Spencer. 

Cream-pink (Deep) — Mrs. Gibbs Box, Constance 
Oliver 

Cream-pink (Pale) — Mrs. Routzahn, Lady Mil- 
ler, Mrs. Hugh Dickson 

Crimson — King Edward Spencer 

Fancy — Afterglow 

Lavender — Florence Nightingale 

Magenta — Menie Christie 

Marbled — May Campbell 

Maroon — Nubian, King Manuel 

Maroon-purple — Arthur Green 

Maroon-red — Brunette, Red Chief 

Mauve (Dark) — Tennant Spencer 

Mauve (Pale) — Mrs. Heslington, Mauve Queen 

Orange-pink — Edrom Beauty, Carene, Helen 
Lewis 

Orange-scarlet — Thomas Stevenson 

Picotee edged (Cream ground) — Evelyn Hemus, 
Mrs. C. W. Breadmore 

Picotee edged (White ground) — Dainty Spencer, 
Elsie Herbert, Martha Washington 

Pink (Deep) — Hercules, Countess Spencer 



20 CULTURE OF THE SWEET PEA 

Pink (Pale) — Elfrida Pearson 

Rose — Marie Corelli, Rosabelle 

Salmon Shades — Stirling Stent, Melba, Barbara 

Scarlet — Dobbie's Scarlet, Scarlet Emperor, Red 

Star 
Striped and Flaked (Chocolate on gray ground) 

— Senator Spencer 
Striped and Flaked (Purple and blue) — Loyalty 
Striped and Flaked (Red and rose) — America 

Spencer, Aurora Spencer, Mrs. W. J. Unwin 
White — White Spencer, Nora Unwin 

VARIETIES OF OPEN AND HOODED FORMS 

Bicolor — Blanche Ferry, Jeannie Gordon 

Blue — Brilliant Blue, Navy Blue 

Blue (Light) — Flora Norton 

Blush — Modesty 

Cerise — Coccinea 

Cream, Buff and Ivory — Zarina, The Honorable 

Mrs. E. Kenyon, Queen Victoria 
Crimson — King Edward VII 
Lavender — Lady Grizel Hamilton 
Marbled — Helen Pierce 
Maroon — Black Knight, Othello 



HISTORY AND EVOLUTION 21 

Mauve — Admiration, Mrs. Walter Wright, 
Dorothy Tennant 

Orange Shades — Henry Eckford, Miss Wilmott 

Picotee edged — Dainty, Lottie Eckford, Phenom- 
enal 

Pink — Prima Donna, Lovely, Katherine Tracy, 
Janet Scott 

Rose and Carmine — Lord Roseberry 

Scarlet — Queen Alexandra 

Striped and Flaked (Chocolate on gray ground) 
— Senator 

Striped and Flaked (Purple and blue) — Princess 
of Wales, Hester 

Striped and Flaked (Red and rose) — America, 
Aurora, Romona 

White — Dorothy Eckford, Shasta, Emily Hender- 
son, White Wonder 

EARLY-FLOWERING VARIETIES 

Bicolor — Earliest of All 

Blue — Le Marquis 

Lavender — Mrs. Alexander Wallace 

Primrose — Earliest Sunbeams 

Salmon-pink — Mrs. William Sim 



22 CULTURE OF THE SWEET PEA 

MARKET VARIETIES 

Open and hooded varieties — Dorothy Eckford, 
King Edward VII, Brilliant Blue, Lady Grizel 
Hamilton, Prima Donna, Blanche Ferry 

Waved varieties — Countess Spencer, Nora Un- 
win, Asta Ohn, King Edward Spencer 

Cultural Requirements 
Site. Sweet peas should be planted 
where they can get the maximum amount 
of sunlight, and the rows should run north 
and south. A free circulation of air is 
beneficial, but the best site is one which is 
not swept by strong winds, which break 
the plants from their supports and injure 
the stems of the plants. Any injury to the 
stem of the plant invariably results in 
smaller flowers and shorter flower stems. 

Soil. Any garden soil is suitable for 
sweet peas, provided it is sufficiently 
drained so that in periods of excessive 
rains the water will not lie upon the sur- 



HISTORY AND EVOLUTION 23 

face about plants, and thus cause them to 
become yellow or to decay at the roots. 
Soil suitable for growing vegetables usu- 
ally gives good results, but extra care in 
the selection and preparation of the soil 
will be repaid in larger flowers, longer 
stems, better colors, and a longer blooming 
period. 

Preparation. The sweet pea is a deep- 
rooting plant, and in order to provide 
suitable conditions so that the effects of 
drought will be overcome, the preparation 
of the soil must be deep and thorough. 
Whatever the nature of the soil, unques- 
tionably the best preparation can be made 
by trenching the soil in the autumn. This 
means turning the soil to a depth ranging 
from 18 inches to as much as three feet. 
In America this method is usually found 
too expensive, and instead a trench 15 to 
18 inches wide along the line of the rows 



24 CULTURE OF THE SWEET PEA 

is used. The soil is removed and replaced 
with prepared soil made by composting 
sod from an old pasture with manure. If 
this method cannot be followed, the top 
soil, to the depth of one foot, can be thrown 
out on one side of the trench and the lower 
soil broken up as deep as possible with a 
pick. If a good application of stable ma- 
nure can be mixed with the subsoil the re- 
sults are better. Often a layer of leaves 
or coarse manure placed in the bottom of 
the deep trench serves to promote drain- 
age. In all cases the trenches should be 
from 18 inches to two feet deep, and it is 
a good plan to work in all the manure pos- 
sible. It does not matter in the fall-prepa- 
ration of the soil if the manure is fresh, 
but of course strawy manure will not do 
except in the bottom of the trench. A 
good application of lime should be made 
while preparing the soil in the autumn. 



HISTORY AND EVOLUTION 25 

Many soils that have been cultivated for 
a long time are acid, and therefore not 
adapted for growing leguminous plants 
such as clover or sweet peas even though 
the soil may be fertile. The lime corrects 
this condition, and also releases plant food 
which otherwise would not soon become 
available. Clay soils are made more open 
and porous by the action of lime. 

Planting 
The Seed. Some primrose and white- 
flowered varieties have white or light-col- 
ored seeds, and some have black seeds. 
The white seeds often rot in the soil, espe- 
cially if they are planted early when the 
soil is cold, or because their germinating 
power has been impaired; also they fre- 
quently split in the pod before harvesting 
and in this condition are likely soon to lose 
their vitality. For the foregoing reasons 



26 CULTURE OF THE SWEET PEA 

it is advisable to sow seeds of this color 
close together and not so deep as the black- 
seeded varieties. 

In some seasons, sweet pea seeds are 
slow in germinating. It is well to exam- 
ine such seeds in order to ascertain their 
condition. If the seeds are found dor- 
mant but still fresh and plump, the seed- 
coats should be cut with a sharp knife and 
replanted; they will then germinate well. 
This difficulty is not confined to the sweet 
pea; some of the other species of Lathyrus 
behave similarly. The trouble usually 
follows a very hot dry season, when the 
seed becomes so excessively ripened as to 
render the seed-coat impervious to water. 
Sometimes, in order to expedite germina- 
tion, the seeds are soaked ; a better method 
for the amateur is that recommended by 
Mr. Hutchins. He places the seed pack- 
ets in moist earth for seven or eight days. 



HISTORY AND EVOLUTION 27 

He then takes them out and examines 
them; the swollen seeds are planted, and 
the others cut with a knife. 

Fall Planting. Often the finest as 
well as the earlier flowers are secured from 
plants the seed of which was sown in the 
fall. South of the latitude of New York 
City this time of sowing can be recom- 
mended. North of this line this method 
cannot always be depended upon unless a 
sandy, well-drained soil is chosen. If the 
water does not lie upon the ground in win- 
ter, and particularly if there is little or no 
freezing and thawing, it is advisable to 
give this method of planting a trial. The 
same preparation of the soil is made as de- 
scribed above, but care must be taken to 
firm the soil so that it does not settle. The 
trench or furrow should be filled so as to 
allow for a slight settling of the soil, thus 
producing a slightly crowning ridge. In 



28 CULTURE OF THE SWEET PEA 

this ridge a little furrow, two inches deep, 
should be made ; or, if preferred, two small 
furrows of equal depth six inches apart 
may be made. The seeds should be sown 
one or two inches apart in these furrows 
and covered so that the surface is slightly 
ridged for drainage. The most important 
point in fall planting of sweet peas is to 
plant so late that the plants do not appear 
above the surface before freezing. In the 
Northern states, if the plants appear above 
the surface of the ground, they will be 
killed by the winter. Seed that have only 
"sprouted," however, will not be harmed. 
In central New York it has been found 
that after November 10 is the best time to 
sow, but, of course, this varies with the 
season. 

After the ground freezes, a mulch of 
manure should be placed over the row, and 
if the snow remains upon the ground all 



HISTORY AND EVOLUTION 29 

the winter the conditions are most favor- 
able. The approach of bright weather in 
spring is the time to examine your sweet 
peas to see whether they are growing. 
Often the manure mulch keeps the soil 
soggy and cold when the bare soil is be- 
coming dry and warm. In such cases re- 
move a portion or all of the mulch, leav- 
ing it between the rows or near at hand, 
so that if there should be a cold wave it 
can be used to cover the plants. The 
plants from fall-sown seed get an earlier 
start than it is possible to secure by sow- 
ing in the spring. The seed of standard 
varieties of sweet peas is so cheap that the 
fall-planting of sweet peas is an effort well 
worth while. 

Spring Planting. As soon as the frost 
is out of the ground and the soil is in work- 
able condition in the spring, a heavy ap- 
plication of superphosphate of lime should 



30 CULTURE OF THE SWEET PEA 

be made and raked in. Care should be 
exercised not to get the soil too loose, and 
for this reason it is best to confine all stir- 
ring of the soil to smoothing the surface. 
Especially is this true with light soils, 
which, if stirred deeply in the spring, must 
be well firmed. Heavy soils that are 
likely to bake may be improved by work- 
ing in a light dressing of old, thoroughly 
rotted manure. 

Sweet peas should be sown as early in 
the spring as the soil is dry enough to 
work, even though it is probable that 
heavy frosts will follow. The writer 
thinks that one reason why even the most 
inexperienced amateur usually has such 
good average results with sweet peas, is 
that he gets his annual "violent attack of 
gardening fever" in early spring, and he 
begins his operations at just the right time 
for sweet peas to go into the ground. 



HISTORY AND EVOLUTION 31 

An essential requirement in growing 
sweet peas is to plant early, while the 
atmospheric conditions are such as to pre- 
vent top growth before the plant has 
started a vigorous root development. The 
result is that, when warmer weather comes, 
the top grows strong and heavy, the plant 
branches out, and throughout the season 
this increased vigor is evident. Experi- 
ments made by sowing seeds every ten days 
from the earliest practicable date until the 
end of May indicate that early planting is 
desirable. 

Depth. If the preparation of the soil 
has been made in the fall, it is advisable 
to smooth the surface of the trench and 
plant in this. When the preparation has 
been made in the spring the soil must not 
be left too loose — a condition that may 
easily occur if a deep trench is made and 
only loosely filled with soil and manure. 



32 CULTURE OF THE SWEET PEA 

One method recommended is to hollow 
out a broad trench, twenty-four to thirty 
inches wide and two inches deep, and then 
sow the seed one inch deep in single or 
double rows. The trench should be kept 
open for six weeks in order to retain the 
water. This system is very good in a gar- 
den where all cultivation is given by hand ; 
but where many rows are grown and cul- 
tivation is done with a horse and culti- 
vator, it is manifestly impossible to make 
or to maintain such a trench. Further- 
more, when horse cultivation is used there 
is difficulty in keeping the young plants, 
if planted below the surface, from being 
covered during the early cultivations. 
Therefore, planting on the level is neces- 
sary in field culture. It is advisable, how- 
ever, in garden culture, to plant so that 
when covered the row will be two inches 
below the ordinary level. 



HISTORY AND EVOLUTION 33 

The seed may be sown in single or dou- 
ble drills as described under fall-planting. 
It is advisable to sow the seeds one or two 
inches apart; if it is suspected that a good 
germination will not result, more seed 
should be sown. 

Thinning. Many persons do not thin 
their plants, and in many cases the reason 
that poor flowers are obtained is because 
of overcrowding. On the other hand, the 
practice of English growers of thinning 
the plants so that they stand several inches 
apart, will not bring successful results in 
our climate. It is difficult to give instruc- 
tions that will apply everywhere; but un- 
der conditions in New York state thinning 
the plants so that they are from four to 
six inches apart has given the best results. 

American sweet-pea growers almost in- 
variably plant sweet peas in rows, but gar- 
den lovers are advised to try the method 



34 CULTURE OF THE SWEET PEA 

of planting sweet peas in small circles or 
even in clumps. Grown in this manner, 
sweet peas may be effectively used in the 
flower garden and in borders. The prepa- 
ration of the soil is similar to that for the 
other method of planting. 

Sowing in Pots for Outdoor Bloom. 
Many English growers practice sowing in 
pots under glass, hardening the plants in 
frames, and planting out. From his own 
experience, the writer is inclined to look 
on this method with favor, especially in 
growing high-priced novelties or varieties 
for exhibition. 

In the greenhouse the seed may be sown 
in February or March. Usually it is best 
to sow about six weeks before one expects 
to plant in the open ground. The seeds 
are sown in three and one-half or four- 
inch pots, using a good compost of rotted 
sod, well-decayed manure or leaf mold, 



HISTORY AND EVOLUTION 35 

and sand. A little of the rougher portion 
of the turf should be placed in the bottom 
of the pot to insure drainage. Fill the 
pots firmly to within one and one-half 
inches of the top and sow four seeds at 
equal distances apart, and cover them with 
an inch of soil. Label each variety care- 
fully as the seed is sown. The pots are 
then placed in a cool greenhouse ; and after 
germination, if the weather is favorable, 
transferred to cold-frames to harden the 
plants. The pots may be placed in cold- 
frames immediately after sowing, but they 
cannot be sown as early as in the green- 
house. The seeds of some of the new va- 
rieties appear to have thick seed-coats, and 
therefore do not germinate readily. Such 
seeds should be clipped with a knife so that 
the moisture can penetrate the seed-coats. 
After the plants appear the pots should be 
kept near the glass so that the plants will 



36 CULTURE OF THE SWEET PEA 

be dwarf and sturdy. Care must be em- 
ployed in watering so that the soil does not 
become sour; and watering the pots in 
frames should be done in clear weather so 
that the plants will dry off before night, 
for if the night is frosty the plants may 
suffer. In severe weather the frames must 
be protected by mats and banked up with 
manure. The frames must be kept well 
ventilated, and as warm weather advances 
the sash should be entirely removed during 
the day. Proper handling during plant- 
ing out will insure success. 

If the plants begin to form tendrils, a 
few twigs should be inserted to support 
the plants. Results of the neglect of this 
important requirement will be apparent 
later in the season. Except when grown 
for market purposes, for which earliness 
is an important consideration, it is advis- 
able for the amateur to delay the sowing 



HISTORY AND EVOLUTION 37 

so that the plants in pots do not become 
tall enough to require much support. The 
usual practice is to plant these pot-clumps 
twelve to eighteen inches apart in the row. 
The entire potful is planted without dis- 
turbing the twigs supporting the plants. 
It is better to pick out the crock from the 
ball since it loosens the tips of the roots 
which, when planted, are encouraged to 
strike down into the soil. Sometimes, the 
roots are long, and therefore are wound 
around the ball of earth in the pot; if they 
are not loosened, they may continue to 
grow in the same manner, thus not estab- 
lishing connection with the soil prepared 
for the plants. It is essential to keep the 
roots growing down into the cooler, 
moister soil. No difficulty will be experi- 
enced in planting sweet peas from pots, 
provided they have been given a good 
watering the day before planting, which 



38 CULTURE OF THE SWEET PEA 

will aid in keeping the ball of earth entire 
when the plants are knocked out of the 
pots. If the soil is dry when the planting 
is done, it will often be advisable to water 
the plants when they are set. Under nor- 
mal conditions, however, this practice is 
not advised. 

The Cordon System. 1 After trans- 
planting, pinch off the tip or growing 
point of the plant and allow only two lat- 
erals to develop. Pinch off all others and 
thereafter allow only two shoots on each 
plant. If the ground has previously been 
well firmed down, the plants will be sturdy 
and short jointed, producing an abundance 
of blossoms. For the cordon system the 
plants should be trained up on tall sticks 
about ten feet high, which have been se- 
curely fastened at their upper end to a 
stretched wire. A good practice is to have 

1 By Frank G. Cuthbertson, Sweet Pea Specialist. 




Fig. i. — Method of growing Sweet Peas for seed in 

England. The vines are trained on tree boughs, 

and the pods gathered by hand. 

View at Dobbie and Co.'s seed farm, England. 



HISTORY AND EVOLUTION 39 

a double row of plants about ten inches 
apart and a double row of stakes or sup- 
ports. If stakes cannot be had, strings 
may be stretched from a line of wire ten 
feet high down to the plants and pegged 
down. The shoots will have to be tied to 
the stakes or strings as fast as they grow, 
thus preventing the breaking of stems and 
blossoms. The tendrils should also be cut 
off, as well as all laterals as they appear. 

By following the cordon system the 
leaves will be very large and the flowers 
will have standards of one and one-half 
or two inches across. 

Supports. Among English sweet pea 
growers there is considerable unanimity 
of opinion that sticks form the best sup- 
port for sweet peas (fig. 1). The replies 
of fifty-two leading experts, published in 
the Sweet Pea Annual for 1907, show that 
forty-three growers favor sticks (gener- 



40 CULTURE OF THE SWEET PEA 

ally hazel sticks), five favor wire netting, 
two favor either sticks or wire netting (the 
netting if new to be painted) , one prefers 
sticks and string, and the remaining one, a 
correspondent from British Columbia, uses 
telephone wire and string. 

In this country, where good twiggy 
boughs can be obtained such boughs un- 
questionably form the best support to use 
since they are the most natural. In many 
places birch boughs can be obtained in 
lengths of twelve to fourteen feet. These 
may be prepared in the lengths desired. 

The height of the support must be de- 
termined by the grower. If the soil has 
been prepared properly and the plants 
look strong, and if the grower waters the 
plants properly and gives them every care, 
then the support. should be six feet high. 
If the soil is only moderately fertile or 
has not been properly prepared, or if the 



HISTORY AND EVOLUTION 41 

grower does not intend to keep all seed- 
pods picked off or cannot water the plants 
in order to overcome drought, the support 
should be kept down to four feet. The 
variety has something to do with the 
height of the support, whatever the care 
bestowed, some varieties being naturally 
dwarfs. 

The sticks should be cut in late winter 
or very early spring so that they are 
rather green and tough enough to bear the 
load until the end of the season. They 
should be inserted in the soil at least a foot, 
because when they are clothed with vines 
to a height of six feet a strong windstorm 
exerts a tremendous leverage on them. If 
the sticks have not been inserted deeply, 
or if they have become dead and brit- 
tle, the row will go down under the force 
of the wind and the great weight of the 
wet vines. In order to guard against dis- 



42 CULTURE OF THE SWEET PEA 

aster, strong stakes are sometimes placed 
every ten feet and wire is run lengthwise 
through the sticks and fastened to the 
stakes. It is desirable to have the sticks 
more bushy at the top than at the base, so 
that they spread out more than at the base ; 
if not naturally so, leaning the sticks alter- 
nately outward will produce this result. 
This method gives greater freedom for the 
vines when they are in flower. 

After the sticks are inserted, a better ef- 
fect is produced if the tops are clipped to 
a level and straggling ends are cut back. 
If the sticks are not "feathered" suffi- 
ciently at the base for the plants to start 
up on them, the clippings from the tops 
may be inserted between the tall sticks. 
Some growers make a practice — and it is 
a good one — of providing a light support 
when the plants are one to three inches 
high, and later placing the tall sticks. For 



HISTORY AND EVOLUTION 43 

the light support they often use old rasp- 
berry canes, in fact, anything of a light, 
much-branched character. This affords 
protection from high winds when the 
plants are small. 

Netting. When other systems of sup- 
porting are to be employed, it is quite im- 
perative to provide a support of small, 
short twigs as soon as the seedlings begin 
to produce tendrils. This method pre- 
vents the rain from beating the small 
plants down, and enables them to get up 
to the other support. In city gardens, 
owing to the difficulty in procuring suit- 
able sticks, wire netting makes a very sat- 
isfactory support. The peas do not cling 
to it so well, but it is cleaner and neater 
in appearance, and thus offers a compen- 
sating advantage. The large mesh (four- 
inch) is preferable; but in many places 
this is not procurable and the ordinary 



44 CULTURE OF THE SWEET PEA 

chicken netting, or fence, is used instead. 
Strong stakes at intervals not to exceed ten 
feet are used to support the netting. One 
advantage of wire netting is that if stakes 
six feet high are used, a forty-two or forty- 
eight-inch strip of netting may be placed 
in position; and, if the season or soil is 
favorable and the peas grow above this, a 
narrow strip of netting may be added or 
a string or wire stretched from stake to 
stake over the row. A well-galvanized 
netting can be used repeatedly for several 
years, and will last longer if taken off in 
the fall and stored. 

String. Another method is to con- 
struct a support of wire and string, or of 
string alone. The ingenious grower can 
construct all sorts of fanciful designs with 
wire and string on posts set not over ten 
feet apart. Sometimes a wooden strip is 
nailed horizontally at the top and bottom, 



HISTORY AND EVOLUTION 45 

but often a wire is used instead. From 
bottom to top, between these horizontal 
strips or wires, a homemade network can 
be constructed. When the peas are grown 
in double drills, the construction described 
above is made on each side in box-like 
form. 

When sweet peas are grown in single 
drills, especially on a considerable scale, 
the best and cheapest support is one made 
by placing stakes at intervals of less than 
ten feet and winding strong cord around 
the row from stake to stake. The strings 
are placed six to eight inches apart, or 
closer if necessary. If the stakes are too 
far apart — ten feet or more — the string 
will stretch after becoming wet or even 
damp, and the plants will fall over. If 
appearance is not an object, anything will 
serve for stakes, e.g., tailings from the 
mills, poles, and the like. If neat stakes 



46 CULTURE OF THE SWEET PEA 

are used, the string method is very good 
for the garden as the vines cling to it bet- 
ter than to wire netting, which furthermore 
becomes hot in the summer. At the end 
of the season, if the stakes are worthless, 
the whole support as well as the vines may 
be burned. 

The foregoing method applies to sweet 
peas grown in rows. Sweet peas are some- 
times grown in clumps and must be sup- 
ported. Here again sticks are often fa- 
vored, especially where the plants occupy 
a circle six feet or more in circumference. 
Wire netting cut in suitable lengths may 
be made into cylinders for clumps of any 
size. 

Henry Eckford recommends a sweet pea 
support consisting of four stakes, each in 
two pieces three feet long. These are 
placed ninety degrees apart around a cir- 
cle and three-foot netting is stretched 



HISTORY AND EVOLUTION 47 

around them. When the peas reach the 
top, if greater height is needed, the upper 
half of each stake is fitted by means of a 
mortise into the top of the one already 
driven and another strip of netting is put 
on. 

An English seedsman advertises sweet 
pea ladders for use in training the vines in 
garden decoration. The ladders are made 
six feet long and six inches wide. They 
are used perpendicularly, the tops being 
fastened to a horizontal wire. Two rows 
are supported by leaning the tops together 
and fastening them to an overhead hori- 
zontal wire. Plants grown in circles may 
be brought together in the center at the 
top where the ladders are fastened to a 
center stake. Sweet pea arches about six 
feet high are sometimes made. 

The ladders can be easily made with 
two No. 10 galvanized wire rose stakes of 



48 CULTURE OF THE SWEET PEA 

the proper length, and some smaller wire 
for the rungs or cross wires. These, of 
course, should never be over six feet high 
or they would seldom be covered. The 
arches can also be made complete, if de- 
sired, by merely making the ladder long 
enough and bending it into the form of 
an arch. 

Cultivation 

Tillage. Sweet peas need frequent 
cultivation. A loose dust mulch upon the 
surface must be constantly maintained in 
order to retain the moisture for the plants. 
Amateurs often fail because they do not 
cultivate their sweet peas, but depend 
upon artificial watering, which will not 
bring the same results as stirring the soil. 
The surface should be kept loose with a 
rake, and if this condition is maintained 
there is usually little need of artificial 
watering. 



HISTORY AND EVOLUTION 49 

Watering. This practice often results 
in more harm than good. During periods 
of drought it may be advisable to apply 
water. If so, apply liberally so that the 
soil is thoroughly soaked. It is also im- 
portant to remember that having begun 
to water, it is necessary to keep it up until 
the rains come. Two or three applications 
a week will probably be required. 

Mulching. A mulch of thoroughly 
rotted manure around the plants will as- 
sist in lessening the effects of a drought; 
or if water is also applied, the mulch will 
enable the plants to get the benefit of it 
by preventing rapid evaporation. 

Dispodding. A long period of bloom 
cannot be had unless the seed-pods are 
consistently picked off. Even the best cul- 
tural methods go for naught unless this 
operation is given careful attention. The 
importance of watering has been over em- 



50 CULTURE OF THE SWEET PEA 

phasized, whereas the true explanation of 
success lies in the removal of all pods as 
soon as the flowers wither. If delayed un- 
til the seed-pods are well developed, their 
removal is of little benefit to the plant. 
If one desires to save seed, it is best to 
mark vigorous plants and save seed from 
them. As the plants usually flower freely, 
few plants are necessary to supply all the 
seeds required by the amateur. All plants 
not required for seed production should be 
kept free of seed-pods so that they will 
continue to produce flowers. Cutting all 
of the best flower spikes does not produce 
the desired results, unless the plants are 
gone over frequently, many short-stemmed 
or inferior flowers will form pods and in 
a very short time the strength of the plant 
will be utilized in developing these in the 
effort to reproduce itself. To obtain good 
flowers for the longest period of time the 



HISTORY AND EVOLUTION 51 

grower must destroy promptly and thor- 
oughly the withered flowers. 

An English sweet pea expert has con- 
cisely summarized sweet pea culture as 
follows : 

"Sweet Pea Culture, condensed in these 
words. Trench deeply; manure liberally; 
plant thinly; stake quickly; water freely; 
dispod promptly." 

Marketing 

Picking. The ideal time to pick sweet 
peas is two or three hours before they are 
needed or are to be placed on the market. 
This length of time is the period the 
blooms should remain in water. During 
this period many varieties will improve in 
size and color, and of course it is desirable 
to have flowers at their best when they are 
to be sold. 

If the flowers are to be shipped to mar- 



52 CULTURE OF THE SWEET PEA 

ket, the time in transit must be added. 
These factors will govern the time of pick- 
ing. It is best, however, to pick in the 
morning or late afternoon. 

The stage at which the flower spikes are 
picked will depend upon the foregoing 
factors, and also upon the weather and 
temperature conditions. The spikes ought 
to be picked when the upper flower is 
about one-half open. 

In picking, a knife or scissors should not 
be used, but the spikes should be pulled. 
A quick side pull, while holding the stem 
near the base, will usually accomplish the 
result without damage to the plant. As 
soon as picked, the flowers should be 
placed in water. Vases about eight inches 
in diameter, and the same in depth, are 
about right, since the stems can be plunged 
six or seven inches. Sometimes eight-inch 
pots are taken and the bottom opening 



HISTORY AND EVOLUTION 53 

plugged up so as to make sweet-pea vases. 
These are excellent because they have the 
best form to keep the flowers in the proper 
position. 

Packing 
Sweet peas are bunched before packing, 
twenty-five flowers usually being put in 
each bunch. If the bunches are made flat 
instead of round, they will pack much bet- 
ter. Tie the stems near the base and 
never near the flowers. A flat box for one 
or two layers of bunches is the best pack- 
age. The corrugated and folding paper 
boxes will probably be found to give the 
best results. It is essential that the 
bunches be packed tight enough to prevent 
bruising. Some make a practice of wrap- 
ping each bunch in wax paper. The boxes 
should be properly lined with paper before 
the bunches are put in. 



54 CULTURE OF THE SWEET PEA 

Exhibiting Sweet Peas 

The foundation for success in raising 
sweet peas for exhibition is laid the previ- 
ous autumn in the thorough preparation 
of the soil, followed by a careful selection 
of varieties, thin planting, and liberal cul- 
ture. In order that good flowers may be 
obtained for exhibition, it is best to remove 
all flowers about a week before the date 
of the exhibition, and to allow only the 
spikes with the longest stems to develop. 
The size of the flowers may be increased at 
this time by the use of ammonia or nitrate 
of soda applied to the soil. 

All varieties subject to scorch or scald 
should be shaded with cheesecloth or tif- 
fany. If such varieties are planted to- 
gether, the shading may be more easily ac- 
complished. The varieties which have 
orange in their coloration — that is, Henry 



HISTORY AND EVOLUTION $5 

Eckford, St. George, and Helen Lewis — 
the salmon varieties, and possibly some of 
the scarlets and blues, should be shaded 
for four to six days previous to the time 
the flowers will be needed. The shade 
should be so arranged that it can be re- 
moved at night. 

The sweet peas having been well grown, 
with stems twelve to fifteen inches long, 
the next consideration is the cutting of the 
flowers; for it is one thing to grow good 
flowers, and quite another, but equally dif- 
ficult, to exhibit successfully. 

Sweet pea flowers, especially for exhi- 
bition, should be cut while dry, preferably 
in the morning or evening. The proper 
stage of development will depend on the 
number of hours that must elapse before 
the judge can pass upon the exhibit. 
Flowers cut the day before exhibiting 
should be taken with the lower flowers 



56 CULTURE OF THE SWEET PEA 

open and the top ones in bud. Those with 
four flowers on a spike may be taken with 
the two lower flowers open, the third flower 
opening, and the topmost one in bud. 
The flowers should be placed immediately 
in cool water and removed to a cool, dark 
room or cellar until they are packed. 
Here they are left until the latest moment 
consistent with their timely arrival at the 
exhibition hall, not more than six or seven 
hours if possible. 

When packing, the stems should be 
squeezed in order to remove surplus water 
and then wrapped in a strip of oiled paper. 
Great care should be exercised not to get 
water on the flowers. Each bunch should 
be wrapped in tissue paper and the 
bunches packed not too tightly as to crush 
the flowers. 

Everything is necessary to insure the 
prompt arrival of the flowers at the exhi- 



HISTORY AND EVOLUTION 57 

bition hall, where they are unpacked and 
loosely arranged so that they may resume 
their natural form after the journey. 

The flowers having been put in water, 
the work of arranging the exhibition vases 
should begin. George W. Kerr, an ex- 
perienced exhibitor, gives the following 
directions for the arrangement of flowers : 

"In staging the flowers never crowd 
them. Let every flower 'speak for itself.' 
Twenty sprays make a nice vase, and the 
best method of arranging them is to start 
by putting some grass (cut two inches 
long) in the mouth of the vase, as this 
helps to keep the stems in position. Each 
stem must be put in separately. Let every 
flower be seen as far as possible and all 
face one way, with the exception of such 
varieties as have the back of the standards 
tinted in coloring other than the ground 
color of the flower, when the position of 



58 CULTURE OF THE SWEET PEA 

such might be judiciously varied. One or 
two pieces of foliage — a little Gysophila 
— or light grass, such as Agrostis neublosa, 
might with advantage be used. But this 
should not be overdone, and only if the 
rules allow of it. 

"In staging a collection of twelve varie- 
ties, they should be placed in three rows, 
the back rows being tiered eight or nine 
inches above the other, and arrange the 
colors so that they do not clash. Even if 
the show schedule does not ask for it, name 
each variety with a neat card placed at the 
base of each vase." 

Two very important points for the ex- 
hibitor to observe are: (1) follow the 
rules as to the number of stems per vase 
and foliage allowed; (2) see to it that the 
flowers are true to name. Varieties of dis- 
tinct colors should be used and those that 
are very nearly like others in the exhibit 



HISTORY AND EVOLUTION 59 

excluded. Finally, in placing the vases, 
it is important not to lose sight of the fact 
that a good color scheme is a great aid to 
success. 



CHAPTER II 

CULTURE OF SWEET PEAS FOR SEEDS l 

Laymen who visit a large seed farm in 
California marvel at the acreage of sweet 
peas in that state and wonder how the 
enormous output will be disposed of. But 
it must be borne in mind that California 
grows fully 75 per cent of the sweet peas 
used all over the world. About 50 per 
cent of the sweet peas grown in California 
are exported. Of these much is sent to 
Great Britain, the remaining 50 per cent 
to Holland, France, Germany, New Zea- 
land, and Australia. The gardening pub- 
lic of Great Britain, aided by the seeds- 
men, quickly realized the possibilities of 
the sweet pea as an exhibition and decora- 

1 By C. C. Morse and Co. of California. 
60 



CULTURE FOR SEED 61 

tive flower. Other countries are now grad- 
ually taking more sweet peas and the fu- 
ture may bring a larger export business. 
In the United States only a small propor- 
tion of sweet peas is grown. However, 
the public is beginning to grow more of 
that flower every year, and especially the 
newer Spencer types. On an everage 
the acreage of sweet peas in California 
is about 2000 acres with about 50 per 
cent Grandifloras, and 50 per cent 
Spencers. The value of this crop to the 
growers is about $250,000. The crop ob- 
tained from an acre of sweet peas varies 
very largely according to season, but an 
average yield of Grandifloras would be 
about 800 lb. per acre; that of a good 
strain of Spencers about 250 lb. per acre. 
Owing to the peculiar formation of the 
floral parts, the Spencers are not so prolific 
as the Grandifloras. In the latter the keel 



62 CULTURE OF THE SWEET PEA 

of the flower is clamped, enclosing the 
stigma and the anthers; whereas in the 
Spencers, the keel is full or open and the 
stigma protrudes farther out than the 
anthers, thus interfering with complete 
pollination. It would be hard to esti- 
mate the value of the sweet pea seed to the 
wholesalers and retailers of the United 
States, but it is safe to put it down to about 
$600,000. There is no acreage of sweet 
peas worth mentioning grown in the 
United States outside of California. A 
few acres of high class varieties are grown 
in England and in the other countries 
above mentioned. Except in cases of 
stock seed of new varieties, no sweet pea 
seed is imported in California. 

When most people think of California 
as a seed growing state, they have the idea 
that it is a land where the only thing the 
grower has to do is to plant and to harvest, 



CULTURE FOR SEED 63 

and that California does the rest. The 
seedman in California, however, has his 
trials and troubles like all others and he 
has all the scope he wants for his practical 
ingenuity; probably there is more need of 
it there than in any other state or country. 
It may surprise many to learn that there 
are comparatively few valleys or parts of 
valleys suitable for sweet peas in Califor- 
nia. This in itself already offers the 
grower a chance to use the best of his skill 
and ingenuity. In California, the sweet 
pea does best in a rich heavy loam or a rich 
sediment soil. Too heavy and too sandy 
soils are unfit for that plant. 

The best climate is one which never gets 
too hot during flowering season, and the 
best results have been obtained in valleys 
where the fog rolls in from the ocean in the 
evening, keeping the air moist and cool. 
A hot spell during blossoming is often 



64 CULTURE OF THE SWEET PEA 

fatal to the crop, especially if it is grown 
on light land ; and if the rainfall has been 
slight even on the heavier lands, the vines 
burn up completely. When the soil is of 
a loamy character and the climate foggy, 
fifteen inches of rain are sufficient to carry 
the crop. 

The land is best when dry plowed, just 
as soon as the previous crop is off in the 
fall. Thus when the rain works through 
the clods the particles of soil crumble and 
become pulverized, leaving the soil in 
good shape for early planting. In Cali- 
fornia it has not been found necessary as 
yet to apply any fertilizer to sweet peas. 
They can be grown year after year on the 
same land, often producing better crops 
each year, provided, of course, that dis- 
eases are kept out. To get the best results 
in California, sow the seeds in November 
or December if possible. As soon as the 



CULTURE FOR SEED 65 

clods can be broken down by a disk plow 
or harrow, the work should be started. 
The peas are drilled in rows about three 
feet apart by a two-horse drill, sowing two 
drills at a time and from eight to fifteen 
pounds per acre. The acreage which can 
be sown per day depends upon many 
things such as the condition of the land 
and the size of the plot to be planted, but 
an average of ten acres per day would be 
about right. The planter is set to place 
the seeds about one inch deep, this being 
deep enough for California conditions. 

When the plants are high enough so that 
the rows may be easily seen, the field is 
cultivated by a two-horse "riding" culti- 
vator; and if the weeds have started, the 
plants are given their first hoeing. Dur- 
ing the months of February, March, and 
April, the cultivators are kept going over 
the field until the meeting of the vines be- 



66 CULTURE OF THE SWEET PEA 

tween the rows prevents further cultiva- 
tion. It is generally necessary to hoe the 
crop three times. 

Sweet peas are never given supports or 
stakes in California. The vines meet in 
the rows and by supporting one another 
soon grow to quite a height. In a good 
season they may grow five or more feet 
high. In California each plant sends out 
a very large number of shoots immediately 
above ground so that the fields are very 
thick and in flowering season are just one 
mass of blossom. 

The most important problem is that of 
"rogueing" and of selection. This is es- 
pecially the case with Spencer sweet peas. 
The stock seed should be right; otherwise 
enormous expense and labor are entailed 
in rogueing the great mass of plants in 
flower, and great damage is done. Should 
some rogues be allowed to seed, the stock 



CULTURE FOR SEED 67 

is not only reduced in value, but the land 
that the variety is grown on is fouled for 
all time. Sweet peas will volunteer for 
five or six years, often longer. It may 
thus readily be seen that it pays the grower 
to be careful of his stock when sweet pea 
land is scarce. Rogueing sweet peas con- 
sists in taking out all wrong colors and 
wrong types. The color rogues are fairly 
easy to see, but it takes a trained eye to 
pick out the type rogues; and this work 
has to be most carefully done. Should a 
Grandiflora plant be allowed to remain in 
a crop of Spencers, it would spoil the lat- 
ter in a short time. The rogues are cut 
out with a knife below the level of the 
ground so that the plant will not sprout 
again and give further trouble. 

The careful grower has his stock seed 
grown and selected carefully before he 
plants his acreage. He knows the pedi- 



68 CULTURE OF THE SWEET PEA 

gree of his stock and if he has done his 
work thoroughly he can depend on a crop 
true to type. 

The season of harvest varies. Cutting, 
which is done with the mower, usually 
commences in July. Judgment must be 
exercised as to the proper time for har- 
vest. The vines are ordinarily cut when 
it is considered that most of the pods are 
ripe. Immediately after cutting, the vines 
are piled on large pieces of canvas which 
are placed on the ground where the crop 
has been growing. These sheets are gen- 
erally forty feet square. When the vines 
are thoroughly dry the thrasher and sepa- 
rator are hauled to the patch and a port- 
able gasoline engine supplies the driving 
power. The fields of sweet peas are so 
planned that the thresher will not by any 
chance let any seed drop elsewhere than 
on the area occupied by the variety. After 



CULTURE FOR SEED 69 

each variety is finished the separator is 
thoroughly cleaned out and run empty for 
a while so that no seed will be left in to 
mix with the next variety to be threshed. 
Stock seed is generally threshed by flail 
in order to avoid all possible chance of 
mixture. After this the seed is taken to 
the cleaning house and put through a se- 
ries of fans and screens to take out all 
chaff and small and broken seeds. 

The raising of new varieties is very in- 
teresting. All careful breeders work on 
the Mendelian principle, and since the 
realization of the importance of these laws, 
there has been less unfixed stock put on 
the market. The following is a brief 
statement of the procedure for raising new 
varieties. The flower to be pollinated 
must be in a very young stage, generally 
a bud before the color even begins to 
show. As the sweet pea blossom sheds its 



70 CULTURE OF THE SWEET PEA 

pollen in the bud stage, the selection has 
to be made carefully. The buds being se- 
lected, the keel is split open with a sharp 
knife and all the stamens are carefully re- 
moved. The stigma is carefully examined 
to see that no pollen has been deposited 
accidentally. Then pollen is carefully 
gathered from the other parent and depos- 
ited with a fine camel's hair brush on the 
stigma of the flower from which the sta- 
mens have been removed. The artificially 
pollinated blossom is now wrapped in a 
paper bag which is securely fastened to ex- 
clude all possibilities of further pollina- 
tion. It is necessary to make a large num- 
ber of such crosses to obtain results, as it 
often happens that a large per cent of the 
flowers thus crossed fail to set seed. The 
seeds from the successful crosses are care- 
fully gathered and planted separately the 
second year (figs. 2 and 3) . No particu- 





Fig. 2. — Trial grounds of C. C. Morse and Co., San Juan, 

Cal. 



t* f ri*nt w ''«<*s«j«*. 




f '~'~ %3 



Fig. 3. — Field of Morse's White Spencer on C. C. Morse 
and Co.'s Sweet Pea ranch at San Juan, Cal. 



CULTURE FOR SEED 71 

lar notice need be paid to the plants of the 
first year's cross ; and all the seeds may be 
saved together. The second year, how- 
ever, it will be found that there is a large 
variety of blossoms. Close inspection is 
then given to each plant to determine 
whether it has the merits desired. Some 
plants will no doubt be found to contain 
special merits; their seeds should be saved 
separately and grown another year or 
two to determine if they will come true 
to type. 

Every careful seed grower must operate 
for his seed peas a trial ground in which 
are grown all varieties for comparison and 
test. A sample of each crop is taken be- 
fore it is shipped to the customer and a 
sample of all selected stock is taken. The 
various samples of each variety are ar- 
ranged together and any novelty of simi- 
lar color is also arranged with the variety 



72 CULTURE OF THE SWEET PEA 

which it is said to supersede. The sam- 
ples are planted alongside each other. 
Trial ground rows are generally about ten 
steps long, and a six-foot space is left be- 
tween the rows. Each sample is given a 
number which is recorded. If rogues ap- 
pear, their percentage is noted. Improve- 
ment in select stock seed is looked for and 
a value put on each novelty. The trial 
ground is an important part of the equip- 
ment of the seed farm, and too much study 
and time cannot be given to it. Points to 
be noted in judging a stock seed are the 
size of flower, length of stem, number of 
flowers on each stem, color, brightness and 
lasting quality, texture of flower, vigor of 
growth, length of blooming period, and 
the amount of seed produced. 

The sweet pea is not an easy crop to irri- 
gate and it can be done only with care 



CULTURE FOR SEED 73 

and judgment. Generally one irrigation 
should be given and that before the pods 
are set on the vines. 



CHAPTER III 

CULTURE OF SWEET PEAS UNDER GLASS X 

The production of sweet peas under 
glass is being extended every year due to 
increase in prominence as a cut flower, and 
hence their economic value in winter. 
Greenhouse sweet peas as a cut flower rank 
third on the market, coming after the roses 
and carnations. They are thus grown in 
nearly every state in the Union, usually, 
however, in the vicinity of large cities. 
Philadelphia, New York, Buffalo, Boston, 
Chicago, Detroit, Milwaukee, Omaha, St. 
Louis, Kansas City, Denver, and a num- 
ber of other large cities offer good mar- 
ket opportunities for winter flowering 

1 Abstract of Commercial Sweet Pea Culture by Ant. 
C. Zvolanek. 

74 



CULTURE UNDER GLASS 75 

sweet peas. In the warmer states sweet 
peas are grown out of doors during the 
winter, requiring but very little shelter. 

For sweet peas under glass it is neces- 
sary to have a suitable house (see Frontis.) . 
The sides of the house should be at least 
eight feet high, the upper being of glass. 
If the houses are but seven feet high, the 
side rows strike the glass when the vines 
are about half grown, thereby giving half 
a crop. The ridge of the house should be 
from twelve to fifteen feet high. The 
higher the vines grow, the more and bet- 
ter flowers. For December and January 
cuttings, large houses are necessary so that 
the sun may penetrate every corner. 
Sweet peas sown in October as, for exam- 
ple, after chrysanthemums, will not bloom 
before February. 

The ideal soil is sandy loam. Red shell 
soil is good if taken about six inches below 



76 CULTURE OF THE SWEET PEA 

the surface; very coarse gravelly soil if 
well fertilized answers the purpose. Soil 
taken from swampy places, provided it is 
not heavy clay, is good, but cannot be used 
the same year. It should be spread out 
about sixteen inches thick on high ground 
and left there to winter over. The rain 
will wash out any alkali which it may con- 
tain. In the following spring, about June, 
compost may be made of this soil. Some 
air slaked lime and coarse bone is added, 
together with the necessary manure. 

Solid beds of good soil two, or two and a 
half, feet in depth are the best. If sweet 
peas follow a tomato crop, which is on the 
wane by the middle of August, the beds 
should be deeply trenched, bringing the 
bottom soil to the surface. In the bottom 
of the trench three inches of decomposed 
cow manure are worked in ; one foot from 
the surface three inches more of the same 



CULTURE UNDER GLASS 77 

material are added. The house is allowed 
to remain in this condition until nearly 
time for sowing the seed. The soil then 
is usually dry and needs to be moistened 
enough to cling together when it is worked 
next time with the spade. This time it is 
necessary to go down one foot and mix 
the top layer of manure with the surface 
soil; then make it as level as possible and 
thoroughly water it with a strong dose of 
liquid horse manure. In about three days, 
depending on the weather, the house will 
be ready for the planting. 

Sweet peas may also be grown on a bench 
with a few inches of soil, but the result will 
be a weak growth and a crop of short 
stemmed flowers. These soon play out, as 
there is not enough soil or food for the 
vines to live on. 

There are a great many varieties of the 
winter flowering type of sweet peas, the 



78 CULTURE OF THE SWEET PEA 

old grandiflora being the best known. Ac- 
cording to Zvolanek the new Winter 
Orchid-flowering sweet peas are preferred 
to the old type. The principal thing is to 
select the best selling colors. In this re- 
spect the Pink and White Orchids seem 
to have no equal for mid-winter flowering. 
Of the white varieties there are the White 
Orchid, Bridal Veil, Venus, and Mrs. M. 
Spanolin. Of those of lavender shades 
the best are Lavender Orchid, Lavender 
Pink, and Lavender Nora, which is a clear 
lavender of the Winter Unwin type. The 
last named has large sized flowers, the 
average of which are as large as any of the 
Orchid-flowering type. In light pink, 
there are Mrs. A. A. Skach, Mrs. J. Manda, 
and Dolansky Orchid. In dark rose there 
are the Orchid Beauty and President Wil- 
son. The best in orange pink is the 
Orange Orchid, and to this the Orange 



CULTURE UNDER GLASS 79 

Nora and Orange Bird are close seconds. 
Both of these are of the Winter Unwin 
type. The colors above mentioned are 
suitable to grow in large quantities. In 
the dark blue, the new orchid-flowering 
Mrs. M. Anderson is commendable, and 
second only to the Blue Jay or the Winter 
Unwin. In red, the Red Orchid is the 
best. All light pink varieties produce 
much brighter colors if grown so as to 
bloom after the middle of January, when 
the weather is sunnier than in December. 
To obtain a good crop of flowers for the 
Christmas trade, seed should be sown any- 
where north of Washington, D. C, be- 
tween the tenth and twentieth of August ; 
this time, too, will depend somewhat on 
the weather. Warm and bright days in 
the fall at the time of sowing will help 
the main crop in maturing early in Novem- 
ber when the price of sweet peas is very 



80 CULTURE OF THE SWEET PEA 

low. On the other hand, if the weather is 
cool and cloudy at the time the seed is 
sown, the flowers will probably be too late 
for Christmas trade. It is much better to 
have the crop in January, as during that 
month and the following months the prices 
are usually as high as during the Christmas 
week. 

When the beds have been well prepared 
the soil is pressed down and raked smooth. 
Rows are then opened at least five feet 
apart and the seed sown about three inches 
apart in the row, and covered to about one 
and a half inches deep. Seeds should not 
be sown in a soil which is too wet and 
sticky. It is better to wait a few days 
until conditions are right. White sweet 
pea seeds, if planted in dry soil and 
watered soon after being sown, will sel- 
dom germinate. After the seed is sown, 
rake the surface of the bed very fine to the 



CULTURE UNDER GLASS 81 

depth of about one inch. This raking will 
make a fine soil mulch on the top, which 
conserves the moisture, besides keeping 
the soil cool, a condition necessary for suc- 
cessful germination. Under these condi- 
tions no watering will be necessary for at 
least ten days or as long as moisture may 
be found about four inches below the sur- 
face. Sometimes three weeks elapse be- 
fore it becomes necessary to water the beds. 
This method encourages the seeds to send 
their roots deep into the soil in the direc- 
tion of more water. Plants with deep 
roots can withstand the hottest days with- 
out damping off, a condition which often 
follows when the moisture is kept on the 
surface. If the soil becomes too dry after 
a while, water well down to the base, keep- 
ing the surface well worked. After sow- 
ing, the temperature should be kept as low 
as possible; and if the seed is sown in 



82 CULTURE OF THE SWEET PEA 

August when the weather is extremely 
warm the glass should be kept white- 
washed as long as the hot weather con- 
tinues. After the seedlings appear above 
ground they may be sprayed several times 
each day during hot spells. 

To prevent slow germination the seed 
may be soaked in water for about fifteen 
hours just before sowing. This will cause 
the seed to soften and swell so that when 
sown they will germinate quickly. Those 
which still remain hard after the soaking 
should be rubbed against a fine flat file, 
taking one seed in each hand and striking 
once or twice over the file just enough to 
cut the hard skin. The seeds treated in 
this way should be dropped back into the 
water, and within another fifteen hours 
they will be soft, swollen, and ready to 
sow. 



CULTURE UNDER GLASS 83 

After the sowing, the greenhouse should 
be kept as cool as possible, admitting air 
day and night as long as the weather will 
permit. The cooler the temperature of 
the house when the plants are started the 
stronger and healthier they become. Late 
in the fall some heat is necessary. The 
temperature at night, however, should not 
be higher than 40 to 44 degrees Fahren- 
heit; otherwise the young plants will be- 
gin to bloom early before the roots have 
had a good start. The winter sweet peas, 
if sown in August or later, and properly 
cultivated, should be at least thirty inches 
high before the blooms appear. Some- 
times during warm and bright days in the 
fall the plants show a tendency to bud 
very early. In this case, the buds should 
be picked off as soon as they appear. 
When the plants are between two and a 



84 CULTURE OF THE SWEET PEA 

half to four feet high, they should all be- 
gin to bud. At this time the temperature 
should be raised every night by one or two 
degrees. If the temperature averages 44 
degrees F., make it 45 degrees the next 
day, and so on until 52 is reached. This 
is the highest and safest temperature for 
the older winter grandifloras at night. 
When in bloom, the temperature may be 
raised to 60 degrees F. during cloudy days 
and 68 during bright days. All the new 
Winter Orchid-flowering sweet peas in the 
first stage need the same treatment as that 
just described above. But as these begin 
to bud and flower the temperature should 
be raised to 55 degrees F. at night, 60 to 
65 for cloudy days, and 70 to 72 during 
bright days. This higher temperature is 
necessary for the new strains, as the flowers 
are larger and the number to a single stem 
correspondingly more numerous ; the addi- 



CULTURE UNDER GLASS 85 

tional warmth prevents the falling of the 
buds and encourages brighter colors. 

After the plants have reached the height 
of about six inches they should be given 
something to climb on. The best and 
cheapest way is to run one wire on the bot- 
tom and another from eight to ten feet 
above each row, connecting these two 
wires with strings as is done in the grow- 
ing of smilax. Strings should also be run 
lengthwise of the row, about every ten 
inches, as the plants advance in growth. 
At the same time it is well, occasionally, 
to help the vines to climb on the strings. 
The upper wire must be the strongest, for 
when the sweet peas are in full bloom they 
are usually ten feet high, and the vines of 
one row one hundred feet long will weigh 
over a ton. If at any time the upper wire 
should break, all the flowers become 
bruised, crooked, and of very little value. 



86 CULTURE OF THE SWEET PEA 

In order to divide the weight, wooden or 
iron supports should be placed under the 
upper wire every eight feet. 

After the sweet peas have been in bloom 
for some time and begin to produce short 
peduncles it is time to feed them a little. 
The best food is liquid or pulverized cow 
or sheep manure. It is doubtful if nitrate 
of soda is beneficial then. During blos- 
soming the house should not be fumigated 
with hydrocyanic gas for although this 
will destroy many insects it will also de- 
stroy most of the buds which are forming. 

It is preferable to pick the flowers in the 
afternoon, as at that time the greatest 
number of flowers are open. Where thou- 
sands of flowers are picked daily, the most 
experienced help should go over the rows 
first, picking only the best blossoms with 
the longest peduncles, ten selected flowers 
to a bunch. The second and less reliable 



CULTURE UNDER GLASS 87 

help are put to pick the second grade of 
blooms, putting twenty-five sprays to a 
bunch; and finally the third hands should 
gather all the crooked and short stemmed 
blossoms. If the flowers are to be shipped 
a long distance to be sold the next day, 
pick all flowers having three or more 
blooms or buds to a stem. As soon as a 
certain number have been picked they 
should be placed in water, but not in deep 
vases or large pails as the blossoms may 
become wet and lose their fragrance. 
After the flowers have stood in water for 
about three hours they are ready to be 
shipped. 

One of the most successful crops to grow 
after sweet peas is tomatoes. In small 
and moderately warm houses, or propagat- 
ing beds, the tomato seed is sown in No- 
vember and then transplanted in small 
pots and repotted several times afterwards 



88 CULTURE OF THE SWEET PEA 

until the plants are finally placed in five- or 
six-inch pots. After Easter the sweet peas 
which are then beginning to play out, are 
replaced by these tomato plants. They 
are planted 16 to 20 inches apart and 
trained to a single stem. By June or July, 
the tomato crop ought to be on the wane 
and the house is at once prepared again 
for sweet peas. Violets are also success- 
fully grown in rotation with sweet peas. 
These should be planted the latter part of 
September. The beds should be five to 
six feet wide, with a space of twelve inches 
on the north side for one row of sweet peas, 
all the rest being planted in violets. Both 
of these flowers may be planted at the 
same time, since the violets, too, need a 
low temperature not over 40 degrees F. 
The sweet peas will grow slowly at first, 
probably not being over three feet in 
height by the last of February. By this 




Fig. 4. — Sweet Peas and Carnations grown in the 
same house. 

Courtesy of Lord and Burnham. 



CULTURE UNDER GLASS 89 

time the violets will have almost finished 
blooming, or at any rate their market price 
will be low. This is the time to discard 
the violets and to raise the temperature to 
suit the sweet peas; and which will pres- 
ently produce a splendid crop. Chrys- 
anthemums or carnations (fig. 4) may also 
be grown with sweet peas. In a house 
with early varieties such as "Golden 
Glow" and "Pacific," the chrysanthemums 
will be all done by October 20th. If 
sweet peas are sown in four-inch pots 
about September 10th, they will be large 
enough to be put in place by the time 
the chrysanthemums are gone. The soil 
should be prepared and the sweet peas 
planted in place at once, so that they may 
begin to bloom by the latter part of Janu- 
ary. Other things may be grown between 
the sweet pea rows, namely, all kinds of 
bulbs and flats with small ferns. 



CHAPTER IV 

DISEASES OF GREENHOUSE SWEET PEAS 

Recent investigations have shown 
that failures with greenhouse sweet peas 
may be readily accounted for. Sickness 
and death, not considering accidental 
death, both in plants as in animals, are due 
either to insects or to certain definite forms 
of parasitic plant life, also known as germs 
or microbes. Sweet peas need plenty of 
air and sunshine and a cool climate. 
These conditions are far from being satis- 
fied in the greenhouse. Plants, like ani- 
mals, when placed in unnatural surround- 
ings, become a ready prey to disease. 
Sweet peas under greenhouse conditions 
are forced to grow in an unnatural way. 

The parasitic fungi which attack sweet 
90 



DISEASES IN GREENHOUSE 91 

peas are minute microscopical forms of 
plant life, devoid of the green matter 
known as chlorophyll. Structurally, a 
fungus consists of one cell or of several 
cells, connected end to end, forming 
threads known as mycelium. The fungus 
gains access to the interior tissue of the 
plant, and deprives the latter of the food 
it needs for its welfare. This action re- 
sults in slow death or in a sudden collapse 
of the affected host. In the case of pow- 
dery mildew, mentioned later, the fungus 
lives on the surface of the leaves, and sends 
delicate suckers into the epidermis to ob- 
tain its food from the tissue of the host. 

Parasitic bacteria are smaller forms of 
life than are the fungi, but their mode of 
attack is not very different. With the ex- 
ception of the large mushrooms, which are 
also fungi, most others are invisible to the 
naked eye and must be studied under a 



92 DISEASES OF THE SWEET PEA 

compound microscope. When grown in 
pure culture, however, they are plainly 
visible as colonies of aggregate individ- 
uals. 

Insects are divided into two classes : one 
class derives its food by sucking the plant 
juices and is known as "suckers" ; the other 
class chews and eats solid parts of roots, 
stems, foliage, or blossoms, and is known 
as "biting." All insects undergo certain 
changes (metamorphosis), beginning as 
larvae and ending as adult beetles, bugs, 
or butterflies. Not all animals which are 
parasitic on plants are insects, as, for ex- 
ample, the eel worm. The latter belongs 
to the Arthropoda of the Animal Kingdom, 
its body being composed of many segments 
with no legs. 

Red spiders and mites, likewise plant 
parasites, are not insects. These belong 
to the Arachnida or true spiders. Books 



DISEASES IN GREENHOUSE 93 

of the same nature as the present work 
generally discuss fungi, bacteria, and in- 
sects under different headings. This 
precedent will not be closely followed 
here, but all three will be taken up from 
the point of view of their economic im- 
portance rather than in the light of their 
systematic relationship. 

As a rule plant diseases do not spread so 
rapidly in the greenhouse as in the field. 
The restrictions of wind currents and the 
lack of easy access of insects are, no doubt, 
factors in keeping in check many diseases. 
There are, however, some indoor condi- 
tions such as moisture and temperature, 
which if not properly attended to, will re- 
sult in great financial loss by favoring the 
spread of disease. 

Upon proper watering depends much of 
the success of crops grown under glass. 
The amount of water and the way it is ap- 



94 DISEASES OF THE SWEET PEA 

plied as well as the amount of moisture in 
the air of the greenhouse may determine 
the presence or absence of disease. A rela- 
tively high percentage of moisture in the 
soil or in the air favors damping off. The 
humidity of the atmosphere in a green- 
house is usually much higher than that out 
of doors. From this it follows that good 
ventilation should be provided. Over- 
watering of sweet peas gives rise to un- 
healthy conditions, especially in cloudy 
weather, when evaporation and transpira- 
tion are arrested. Thus the soil becomes 
flooded with water which interferes with 
the respiration of the roots and the plants 
become more susceptible to diseases which 
may be present in the soil in the green- 
house. An excess of moisture in the air 
also favors the development and spread 
of the powdery mildew. During bright 
sunny weather there is little danger from 



DISEASES IN GREENHOUSE 95 

overwatering, since transpiration and 
evaporation are then very active. What 
is true of "damping off" and the mildews 
is also true for root knot. The minute eel 
worms cannot thrive unless there is suffi- 
cient moisture in the soil. Neither can 
they thrive in soils that are flooded, since 
they must have air to live. This is taken 
advantage of in open fields where root 
knot is controlled by flooding the land. 
Overwatering, or any form of injudicious 
watering, is no doubt an important factor 
in predisposing the sweet pea plants to the 
attacks of Thielavia, Rhizoctonia, Chae- 
tomium, and Fusarium root rots. It is 
therefore well to provide some means of 
drainage, especially where the beds are 
solid and in the ground. It is a good 
practice to lay at the bottom of the beds 
from one-half to one foot of ashes or a 
layer of broken bricks or crushed stones. 



96 DISEASES OF THE SWEET PEA 

This will help to drain off the excess of 
water likely to be applied by unskilled or 
inexperienced help. 

Water is not the only important factor 
in controlling or increasing fungous pests 
under glass. Temperature also plays an 
important role. Damping off of green- 
house sweet peas is best controlled by 
keeping the greenhouse at a temperature 
of 50 to 60 degrees F. A temperature of 
80 to 90 degrees F. with a high moisture 
content of the air will cause all young 
seedlings to damp off, if the fungus is 
present in the soil. It is doubtful if tem- 
perature greatly influences the control of 
collar rot, although a temperature of 90 
degrees will be more favorable to the fun- 
gus than a temperature of 50 degrees F. 
Nevertheless, a low temperature will not 
considerably check this disease when it 
once gets a start. In greenhouses where 



DISEASES IN GREENHOUSE 97 

collar rot has become established, steriliza- 
tion of the soil is the only remedy. Sweet 
peas grown in the greenhouse are subject 
to moisture conditions quite different from 
those grown outdoors. Natural light is 
less in winter, and in order to induce 
growth under adverse conditions heat is 
used as a stimulant. This produces plants 
readily susceptible to disease. As these 
difficulties cannot be avoided, it is essen- 
tial to start with sterilized soil in the 
benches. 

Most sweet pea growers do not change 
their greenhouse soil every year. As time 
goes by, and the crop is grown successively 
in the same place, the soil soon becomes 
sour. This condition naturally tends to 
encourage the development of a parasitic 
flora in the soil which is detrimental to 
sweet pea culture. 

The following is a quick method to de- 



98 DISEASES OF THE SWEET PEA 

termine soil acidity, based on the use of 
litmus paper, devised by Mr. J. E. Har- 
ris, 1 who found that some kinds of litmus 
paper are not suitable. Experiments have 
shown that Kahlbaum's litmus paper is the 
best for the purpose. It is so sensitive that 
it is necessary to leave it in contact with 
the soil particles only for a moment or two. 
Soil only very slightly acid will change the 
litmus paper to a distinctly red color. 
Acid soils are easily corrected by the use 
of lime. The latter favors Thielavia rot 
but this is no consideration where sterilized 
soil is used. 

RHIZOCTONIA ROOT ROT 

Corticium vagum B. and C. 

No mention is made in literature of a 
Rhizoctonia disease of sweet peas, al- 

1 Harris, J. E., Soil Acidity and Methods for its De- 
tection. Science. N. S. XL 1491-493, 1914. 




Fig. 5. — Root Rot caused by Rhizoctonia. 
Healthy and diseased plants. 




Fig. 6. — Root Rot caused by Rhizoctonia. 
To the right the soil was inoculated 
with the fungus, resulting in no ger- 
mination; to the left, check. 



DISEASES IN GREENHOUSE 99 

though the same fungus is recorded on 
other hosts. During the winters of 1911 
and 1912, it was found by the author on 
greenhouse sweet peas from different lo- 
calities. Through correspondence, Pro- 
fessor A. D. Selby reports its presence in 
Ohio; Dr. W. G. Sackett, in Colorado; and 
Professor E. C. Stackman, in Minnesota. 
There seems no doubt that the Rhizoctonia 
root* rot of sweet peas is much more wide- 
spread than is reported. The nature of 
the trouble is unknown to the growers. 
Outdoors, Rhizoctonia also attacks the gar- 
den pea, bean, lettuce, carrot, celery, cow 
peas, and a number of other hosts. 

Symptoms. Severely infected plants 
have practically no root system (fig. 5) . 
In slightly infected plants, only one or two 
rootlets may be destroyed. The fungus 
produces a browning effect of the root be- 
fore total destruction sets in. In very 



ioo DISEASES OF THE SWEET PEA 

early stages of the disease infected seed- 
lings are seen to have a wilted appearance ; 
as the disease progresses they fall over and 
collapse. The fungus is not often con- 
fined to the roots alone. It frequently 
works its way up to the stem, producing a 
constricted area which marks it off from the 
healthy part above. The fungus being a 
soil organism is usually introduced with 
manure; infection may take place at any 
part of the roots, or at the lower end of the 
stem. When the latter is the case, reddish 
sunken spots are observed at the base of the 
stem. It seems that Rhizoctonia is pri- 
marily a seedling disease of the sweet pea, 
although older plants too are found to be 
affected with the same fungus, but are not 
killed outright since they linger for a con- 
siderable time without producing blossoms 
of commercial or ornamental value. 



DISEASES IN GREENHOUSE 101 

Pathogenicity. The pathogenicity or 
the disease producing power of the sweet 
pea Rhizoctonia may be readily proven by 
planting disinfected seeds in sterile soil 
and also in pots which were inoculated 
with a pure culture of the fungus (fig. 6) . 
The best material is a culture which has an 
abundance of sclerotia. 

The parasite has two stages — the Rhi- 
zoctonia, and the sclerotial stages. The 
Rhizoctonia stage consists of long and 
narrow mycelial branches varying in color 
from hyaline to reddish brown (fig. J a) . 
These threads are either imbedded in the 
substratum in which they grow, or they are 
aerial, depending on the media on which 
the fungus is grown. These mycelial 
threads are the most active and are more 
concerned in the parasitism of Rhizoc- 
tonia. The sclerotial stage consists of 



102 DISEASES OF THE SWEET PEA 

numerous sclerotia which are made up of 
closely interwoven short barrel-shaped 
hyphae (fig. jb) . 




fig. 7. a young hyphce of Rhizoctonia from sweet pea. 
b barrel-shaped hyphce from sclerotia OF the same 



FUNGUS. 



Rhizoctonia solani Kuhn produces only 
micro or small sclerotia, whereas Corticium 
vagum B. and C. produces macro or large 
sclerotia. After repeated attempts the 
Corticium or perfect stage of the sweet pea 
Rhizoctonia could not be obtained in pure 
culture. This accords with the findings of 




Fig. 8. — Pure culture of the Sweet Pea 
Rhizoctonia, showing large and 
smaller sclerotia of the fungus. 




Fig. 9. — Pure culture of Fusarium 

lathyri, the cause of Sweet Pea 

Wilt. 



DISEASES IN GREENHOUSE 103 

Shaw * and Rolfs, 2 who could not obtain 
the perfect stage on culture media but 
found it several times on the host. How- 
ever, as the sweet pea Rhizoctonia pro- 
duces macro-sclerotia (fig. 8) , and as al- 
ready pointed out by Shaw, the macro- 
sclerotia produce the Corticium stage, the 
sweet pea organism is therefore referred to 
as Corticium vagum B. and C. 

Pathological Conditions of the 
Host. Practical men, no doubt, like to 
know what happens to the host plant when 
it is attacked by the fungus. Rhizoctonia 
when attacking hosts other than the sweet 
pea, is found to parasitize the cambium 
layer or growing part of the plant. With 
the sweet pea, conditions are somewhat 

1 Shaw, F. J. F., The morphology and parasitism of 
Rhizoctonia. Mem. Dept. Agr. India, Bot. ser. IV : 

115-153. 1 9 12 - 

2 Rolfs, F. M., Potato failures, a second report. 

Colo. Agr. Expt. Station Bui. 91, 1904. 



104 DISEASES OF THE SWEET PEA 

similar. The fungus attacks the phloem 
or food tracts and makes its way into the 
parenchyma cells as well as to the epider- 
mal cells. The effect produced is loss of 
turgidity, wilting, and early collapse of 
the host. 

Growers should not fail to recognize 
Rhizoctonia root rot in its initial stage. 
To allow this fungus to get a foothold 
would mean the ruin of an otherwise prom- 
ising crop. 

CH^TOMIUM ROOT ROT 

Chcztomium spirochete Patt. 

In the autumn of 1912, Professor A. C. 
Beal of Cornell University sent me for 
diagnosis diseased specimens of green- 
house sweet peas. The trouble was read- 
ily located in the roots. A fungus was 
found invading the interior tissues of the 
roots, but no fruiting stage of any kind to 



DISEASES IN GREENHOUSE 105 

help identify the fungus could be dis- 
covered. Crush cultures were made at 
once from the diseased material. Some 
forty poured plates of nutrient agar were 
made. In five days a pure culture of a 
fungus appeared in all the plates with the 
exception of one, which showed a Fusa- 
rium. The cultures were watched closely 
and in two weeks perithecia developed. 
The fungus proved to be an ascomycete 
belonging to the genus Chaetomium, and 
determined by Mrs. Flora Patterson :as 
C. spirochete Patt. In mid winter of that 
same year, more diseased specimens were 
sent in to my laboratory by a grower in 
Illinois. These were greenhouse plants 
showing the same symptoms as those ob- 
served on the plants sent by Professor Beal. 
Cultures made from this material gave the 
typical fungus Chsetomium spirochete. 
A search through the literature showed that 



io6 DISEASES OF THE SWEET PEA 

several species were recorded but none 
were stated to be parasites. 

Symptoms. At the first glance Chaeto- 
mium root rot is difficult to tell from 
Thielavia. Infected plants lose their 
green color, become pale and yellow, and 
cease growing. The root system is usu- 
ally found wanting or partly destroyed. 
The disease seems to be primarily a seed- 
ling trouble. 

Pathogenicity. The fact that a pure 
culture of Ch&tomium spirochete was ob- 
tained from numerous platings of dis- 
eased material from two different states 
at once led to the supposition that the or- 
ganism was the cause of the disease. In- 
oculations with pure cultures of the fun- 
gus into healthy seedlings proved the 
organism to be a weak parasite, favored 
by an excess of moisture in the soil. 

The Fungus. The mycelium of the 



DISEASES IN GREENHOUSE 107 

fungus is hyaline, closely septate, and 
branched (fig. 10a) when grown in the 
substratum of the media. The aerial my- 




fig. 10. o showing mycelium of Chcetomium Spirochete. 
b hairs, c and d asci. e ascospores. 

celium consists of long unbranched fila- 
ments varying in color from light to deep 
lemon. The yellow seems to be produced 
within the fungus hyphse which later is 
also transmitted to the media. In pure 
culture the fungus produces its perithecia 



108 DISEASES OF THE SWEET PEA 

or fruit bodies in about two weeks after 
sowing. These perithecia are covered 
with dark hair-like appendages. The 
hairs are straight or coiled at the apex 
and septate at unequal intervals, and cov- 
ered with very minute pointed warts (fig. 
io£). The asci are very evanescent and 
can only be seen in very young cultures 
just as the perithecia are forming. In old 
cultures the ascus wall is easily ruptured 
so that it is difficult to make out the ar- 
rangement of the ascospores within. 
There are eight ascospores in each ascus 
(fig. 10c and d) . The ascospore is apicu- 
late (fig. \oe) at both ends. Its wall is 
smooth, light brown when young and dark 
when old. It will germinate readily 
in distilled water or in any nutrient 
broth. 

Chsetomium root rot is not likely to 
prove troublesome in greenhouses where 



DISEASES IN GREENHOUSE 109 

the ventilation and the watering are prop- 
erly attended to. 

FUSARIUM ROOT ROT 

Fusarium lathyri Taub. 

There is no record in the mycological 
literature of a Fusarium disease of the 
sweet pea. Numerous complaints from 
florists showed that sweet peas often did 
not grow well under glass because of a 
root rot which developed early and in some 
cases destroyed the entire planting. Cul- 
tures made by the writer from infected ma- 
terial or from the infected soil gave in each 
case a pure culture of Fusarium. 

Symptoms. The disease produces a 
sudden flagging of the leaves accompanied 
by sudden wilting and collapse of the seed- 
ling. Usually a fair percentage of the 
seeds germinate and the plants reach the 



no DISEASES OF THE SWEET PEA 

height of about eight to ten inches when 
they are attacked by the fungus. If the 
collapsed seedlings are allowed to remain 
on the ground, the dead stems will soon be 
covered with the sickle shaped spores. 
Eventually the dead tissue rots and dis- 
integrates and is soon invaded by small 
fruit flies which now begin to distribute 
the spores of the fungus to different places 
in the same house. 

Pathogenicity. The pathogenicity of 
this fungus is readily proven by inoculat- 
ing a pure culture (fig. 9) of the fungus 
into healthy seedlings planted in sterile 
pots and soil. The seeds germinate and 
grow up to a height of seven to eight inches 
and then succumb to the parasite which 
was artificially introduced into the soil 
(fig. 11). 

The Fungus. The mycelium of the 
fungus is hyaline, branched and septate. 




Fig. ii.— Fusarium Wilt or Root Rot. At left, healthy 
plant; at right, infected. 



DISEASES IN GREENHOUSE ill 

At an early age the hyphae begin to form 
chlamydospores or resting spores. These 
are round hyaline bodies often filled with 
oil globules and are formed in the center 
of the hypha. Usually also the chlamydo- 
spores are born at the tip end of the hyphae 
in chains of twos, threes, and even fours. 
Old cultures consist largely of a mass of 
chlamydospores. There are also two other 
types of spore forms, and these appear as 
early as the third day in the pure culture. 
These are micro-conidia or small one-celled 
spores, and macro-conidia or large cycle- 
shaped spores, varying from two-celled to 
four-celled. The usual form is three- 
celled. In old cultures the macro-conidia 
shrink so that the septa become slightly 
prominent. These old macro-conidia soon 
lose their protoplasm, or they break up, 
presenting a granular appearance. In 
young cultures the outer wall of the chla- 



112 DISEASES OF THE SWEET PEA 

mydospores is smooth, but in old cultures 
it becomes slightly warty or covered with 
minute points. No perfect stage has been 
found to accompany this fungus, either on 
the host or in pure culture. 

Fusarium root rot is a serious disease 
which threatens to undermine the growing 
of greenhouse sweet peas. The grower 
should do everything possible to prevent 
its introduction into the house. In places 
where this disease has already gained a 
foothold, soil sterilization becomes a nec- 
essary part of sweet pea culture under 
glass. 

THIELAVIA ROOT ROT 

Thielavia basicola Zopf. 

In 1912, Chittenden 1 was asked by the 
National Sweet Pea Society of England to 
investigate the "streak" disease of the 

1 Chittenden, F. J., Diseases of the Sweet Pea, Sweet 
Pea Annual: 14-24, 1912. London. 




Fig. 12. — Root Rot caused by Thielavia. 

Roots of diseased and healthy plants 

of the same age compared. 



DISEASES IN GREENHOUSE 113 

sweet pea. In his report before that so- 
ciety, Chittenden gives an accurate de- 
scription of the "streak," so that there can 
be no doubt that he had the disease well in 
mind, that is, he described it as a stem dis- 
ease. Chittenden, however, attributed 
"streak" to Thielavia basicola Zopf. In 
this Chittenden erred, for streak has since 
been found to be caused by a bacterium. 
Massee, 1 too, made the same mistake, for 
he also considered Thielavia as the cause 
of "streak." Streak however is different 
from Thielavia root rot. 

Symptoms. Plants severely infected 
with Thielavia have practically no root 
system, since the roots are destroyed by the 
fungus as rapidly as they are formed (fig. 
12) . All that is left of the root system is 

2 Massee, George, A disease of sweet peas, asters and 
other plants. Roy. Bot. Gard. Kew Bui. of Misc. In- 
form. No. 1:44-52, 1912, London. 



114 DISEASES OF THE SWEET PEA 

a charred blackened stub. The fungus 
sometimes works upon the stem to a dis- 
tance of two to three inches above ground. 
It is probably due to this that some work- 
ers have mistaken this disease for the 
"streak." Although their root system is 
destroyed, affected plants seem to lin- 
ger for a long time. Diseased plants, 
however, cease growing, and maintain 
a dwarfed sickly appearance (fig. 13). 
These are useless for any purpose, as they 
fail to bloom and merely contaminate the 
beds by their presence. 

Pathogenicity. Healthy seedlings 
may be readily infected by placing a pure 
culture of the fungus in the soil. In two 
to three weeks the roots of the infected 
plants will be thoroughly diseased. Over- 
watering does not seem to be a necessary 
factor in infection, although it no doubt 
helps to weaken the plants and further 




Fig. 13.— Root Rot caused by Thielavia. A healthy 
plant contrasted with a diseased plant. 



DISEASES IN GREENHOUSE 115 

aids the fungus in its destructive work. 
Thielavia basicola also attacks a number 
of hosts other than the sweet pea. Pure 
cultures of the fungus obtained from cow- 
pea, violets, parsnip, and tobacco, when 
inoculated on the sweet pea will readily 
infect the latter. This shows that the dis- 
ease will cross from other hosts to the sweet 
pea and vice versa. 

The Fungus. The mycelium of Thie- 
lavia basicola is hyaline, septate and 
branched. The mycelium becomes some- 
what grayish with age. Three kinds of 
spore forms are produced — endospores, 
chlamydospores, and ascospores. Endo- 
spores are so called because they are formed 
inside a special thread of the mycelium 
(fig. 14^). This is the spore form that 
commonly occurs in pure cultures of arti- 
ficial media and on the host. The endo- 
spore case is formed on terminal branches 



n6 DISEASES OF THE SWEET PEA 




fig. 14. a Endospores. b c Chlamydospores breaking 
up into individual spores, d Chlamydospores un- 
broken, f Ascospores. e single perithecium. 

with a somewhat swollen base and a long 
tapering cell. The endospores are formed 
in the apex of this terminal cell and are 
pushed out of the ruptured end by the 
growth of the unfragmented protoplasm of 
the base. They are hyaline, thin walled, 
and oblong to linear in shape. The chlam- 



DISEASES IN GREENHOUSE 117 

ydospores (fig. 14^ to d) are thick walled, 
dark brown bodies, borne on the same my- 
celium as the endospores. This type of 
spore is formed in great abundance on the 
host and particularly within the affected 
tissue. The ascospores (fig. 14/) are len- 
ticular in shape and are borne in asci (or 
sacs) within black perithecia (fig. 14^) . 
This stage, however, has not been found on 
the sweet pea or in pure culture. 

Thielavia is perhaps next in importance 
to Fusarium root rot. The fungus is 
often introduced with manure or more 
commonly with diseased violets, since this 
flower is profitably grown in conjunction 
with sweet peas. 

Growers, therefore, cannot be too care- 
ful in trying to keep out Thielavia from 
the greenhouse. 



n8 DISEASES OF THE SWEET PEA 

POWDERY MILDEW 

Microsph&ra aim (Waller) Salm. 

The sweet pea mildew was described by 
Massee x as being prevalent in England. 
Erisiphe polygoni was thought to be the 
cause both of the sweet pea and the garden 
pea mildew. In the United States, Pro- 
fessor Stewart 2 was the first to record the 
finding of powdery mildew on sweet peas 
in the United States. However, Stewart 
did not find the perithecial stage which 
would help in the determining of the 
fungus. 

Powdery mildew is a very prevalent dis- 
ease on greenhouse sweet peas, although 
it is also very common on out-of-door 
plants. The fungus which causes mildew 

1 Massee, George, Fungoid diseases of the sweet pea, 
Sweet Pea Annual: 20-21, 1906, London. 

2 Stewart, F. C, Notes on New York plant diseases. 
New York (Geneva) Agr. Expt. Station Bui. 328:394, 
1910. 




Fig. 15. — Powdery Mildew, healthy and diseased leaves. 

Notice the white covering of the affected leaves, due to the growth 
of the mildew fungus on the surface of the former. 




Fig. 16. — Germinated sclerotia of the Sweet Pea 
Sclerotinia which had wintered outdoors. 



DISEASES IN GREENHOUSE 119 

grows on the surface of the leaves, thus 
giving them the white powdery appearance 
(fig. 15) . Affected leaves eventually lose 
their green color, shrivel and fall off pre- 
maturely. The perfect stage of this fun- 
gus is found on fallen and dead leaves. 
Powdery mildew is perhaps universally 
found in every greenhouse where sweet 
peas are grown. It is worse in over- 
watered houses, and in overheated houses 
with excess of moisture. Powdery mil- 
dew is perhaps the easiest disease to con- 
trol. 

STEM OR COLLAR ROT 

Sclerotinia libertiana Fckl. 

Observations seem to indicate that this 
disease is limited to sweet peas grown un- 
der glass. A special effort was made to 
find this disease outdoors, but without suc- 
cess. Under certain conditions unfavor- 



120 DISEASES OF THE SWEET PEA 

able to the host this fungus may attack a 
variety of plants in the open. That this 
fungus has not been found to attack sweet 
peas out of doors does not preclude its ap- 
pearance in the field at any time in the fu- 
ture. 

Symptoms. Collar rot is usually a 
seedling disease which causes "damping 
off." It is most severe in poorly venti- 
lated houses or in beds which are over- 
watered and lack the proper drainage. 
The disease does its work quickly. Af- 
fected plants first show a wilting of the 
tip and flagging of the leaves, and then the 
seedling falls over and collapses (fig. 17) . 
The fungus, Sclerotinia libertiana, al- 
though a soil organism, cannot attack the 
roots of its host. The parasite penetrates 
the collar of the stem, completely invad- 
ing the inner vessels, thus cutting off the 
upward flow of water from the roots to the 



DISEASES IN GREENHOUSE 121 

parts above. Plants which have recently 
died have a water soaked appearance, and 
later covered by a white weft of fungus 
mycelium, and by sclerotia which appear 
irregularly on or within the affected stem. 

Pathogenicity. The pathogenicity of 
this fungus may be readily established by 
inoculating healthy seedlings with a pure 
culture of the fungus. The latter is easily 
re-isolated and the disease produced at 
will. Moisture is the main factor in fa- 
voring infection. 

The Fungus. Sclerotinia libertiana, is 
a fungus too well known to plant patholo- 
gists and even to practical growers to re- 
quire much description. Under green- 
house conditions, the same fungus causes a 
serious disease on lettuce, cucumbers, to- 
matoes, violets, and many other plants. 
When grown on artificial media, there are 
no differences observed on the different 



122 DISEASES OF THE SWEET PEA 

strains isolated from the sweet pea, lettuce, 
cucumbers, tomatoes or violets. More- 
over, any one of these strains will produce 
a disease on any of the hosts enumerated. 
When the sclerotia, after being placed out- 
doors in the cold to over winter, are taken 
in and placed on moist sand kept at room 
temperature, they germinate and produce 
the typical grayish stalks with their apo- 
thecia or fruit bodies (fig. 16) . The latter 
contain the asci in which are the ascospores 
of the fungus. 

Like Thielavia basicola, and because of 
its omnivorous nature, the fungus Sclero- 
tinia libertiana may prove a great draw- 
back to the culture of greenhouse sweet 
peas. The parasite is usually carried with 
the manure or may be introduced on other 
diseased plants. Failure to recognize col- 
lar rot or carelessness in maintaining 



DISEASES IN GREENHOUSE 123 

proper conditions in the house may entail 
serious losses to the grower. 

ROOT KNOT OR EEL WORM 

Heterodera radicicola (Greef) Muller 

Root Knot, {nematode galls) no less 
important than Rhizoctonia and Fusarium 
root rots, causes great loss to greenhouse 
sweet peas. It does not, however, produce 
a damping off in young seedlings. It 
seems very probable, too, that root knot 
in the case of the sweet pea opens the way 
to the attacks of Rhizoctonia and several 
other root troubles, producing also the 
greatest amount of damage in light sandy 
soils. 

Symptoms. The disease is character- 
ized by swellings on the roots. These are 
either small knots formed singly, in pairs, 
or in strings, thus giving the affected root 



124 DISEASES OF THE SWEET PEA 

a beaded appearance; or else the swellings 
are very large (fig. 19) so as to be mistaken 
for bacterial nodules, which occur nor- 
mally in great abundance. Root galls, 
however, cannot be mistaken for legume 
nodules, since the latter in the case of the 
sweet pea are lobed and are attached at one 
end (fig. 18) ; whereas, the root galls pro- 
duce a swelling of the entire surface of the 
part affected. Infected plants usually 
linger for a long time, but they can be dis- 
tinguished by a thin growth and yellow 
sickly looking leaves and stems. 

Distribution. The eel worm of the 
root knot, as it is more often called, seems 
to be of wide distribution, being found 
in Europe, Asia, Africa, Australia, and 
both North and South America. Al- 
though it is found in most parts of the 
world, there are many localities in which 
the pest has never been known. 




Figs. 1 8, 19. — Root knot of Sweet Peas, a root trouble which 
may be mistaken for the true legume root nodules. 

The insert cut in the top left-hand comer shows the normal root nodules 
of the Sweet Pea formed by nitrogen-fixing bacteria. 






1 



DISEASES IN GREENHOUSE 125 

Life History. The eel worm is a very 
minute organism seldom exceeding one- 
twenty-fif th of an inch in length, and since 
it is semi-transparent, it cannot be easily 
detected with the naked eye. In search- 
ing for eel worms, endeavor to break a fresh 
knot. Close examination will usually re- 
veal two types of worms : a spindle shaped 
worm, the male, and a pearly white pear 
shaped organism, the female, firmly em- 
bedded in the gall tissue. The female is 
very prolific, depositing no less than 400 
to 500 eggs during her lifetime. The eggs 
are whitish semi-transparent bean shaped 
bodies and too small to be noticed without 
the aid of a magnifying glass. The time 
which elapses until the eggs hatch depends 
largely upon weather conditions. With 
warm days the eggs hatch sooner than in 
colder weather. Upon hatching, the 
young larvae either remain in the tissue of 



126 DISEASES OF THE SWEET PEA 

the host plant in which they have emerged, 
or, as is more often the case, leave the host 
and enter the soil. This is the only period 
during which the worms move about to any 
great extent in the soil, where they either 
remain for some length of time or immedi- 
ately penetrate another root of the host. 
The nematodes in most cases become com- 
pletely buried in the root tissue, establish- 
ing themselves in the soft cellular struc- 
ture which is rich in food. The head of 
the worm is provided with a boring appa- 
ratus consisting of a sharply pointed spear, 
located in the mouth; this structure not 
only aids it in getting food but is also 
valuable in helping the young worms to 
batter through the cell walls before becom- 
ing definitely located. The two sexes 
during development are indistinguishable 
up to fifteen or twenty days, both being 



DISEASES IN GREENHOUSE 127 

spindle shaped. In the molting or shed- 
ding of the skin, there is a marked change 
in the case of the female, especially in the 
posterior region of the body, which no 
longer possesses a tail-like appendage. 
Fertilization occurs soon after this molt, 
and many radical changes occur in the 
shape and structure of the organization of 
the worm. The fertilized female in- 
creases rapidly in breadth and becomes a 
pearly white flask- or pear-shaped indi- 
vidual. This creature is far from being 
worm-like and may therefore be over- 
looked by one unfamiliar with the life his- 
tory of the eel worm. The adult male is 
much like that of the larvae, being spindle 
shaped in outline. The male does not 
cause as much damage to root tissue as the 
female, and its purpose in life seems to be 
only that of fertilizing the female, for 



128 DISEASES OF THE SWEET PEA 

after this function has been performed it is 
quite probable that the male worm takes 
no more food. 

Omnivorous Nature of the Eel 
Worm. Root knot injury is not confined 
to sweet peas alone. There are two hun- 
dred and thirty-five species of plants 
known to suffer from it. This number in- 
cludes all the important families of flow- 
ering plants, gymnosperms, and ferns. Of 
the greenhouse plants practically all are 
subject to root knot. Violets, carnations, 
chrysanthemums, tomatoes, cucumbers, 
and lettuce are often ruined by this pest. 

Among the plants which are not affected 
by eel worm are the following : crab grass, 
red top, Johnson grass, rye, corn, perennial 
rye grass, timothy, and Zinnia. For the 
purposes of greenhouse rotation none of the 
foregoing plants is of any value. Should 
root knot attack sweet peas outdoors, how- 



DISEASES IN GREENHOUSE 129 

ever, especially where they are grown on a 
large scale for seed purposes, rotation of 
crops will have to be resorted to. 

thrips ' 
Heliothrips hemorrhoid alts Bouche 

The damage done to the sweet pea by 
Thrips is confined mostly to the foliage. 
Thrips feed by sucking on the juices of the 
sweet pea plants. New places and new 
leaves are continually attacked so that the 
affected parts are full of tiny pale spots. 
In severe attacks the spots unite and form 
regular white blotches. Ordinarily it is 
on the under surface of the leaves that the 
mites feed, but when they become very 
numerous they also migrate to the upper 
surface. Both sides of the affected foliage 
thus become covered with minute drops of 

1 For a more detailed technical description, see Bull. 
64 Bur. Ent. U. S. Dept. Agr. 



130 DISEASES OF THE SWEET PEA 

a reddish fluid secreted by the thrips. As 
these drops dry they gradually turn black. 
As the attack progresses, the leaves lose 
all their green color, become limp, and 
drop off. 

Life History of Thrips. An adult 
thrip is about one-twenty-fourth of an inch 
in length, and is dark brown in color, with 
the tip of the body somewhat lighter. The 
female deposits her eggs within the leaf 
tissue, and these hatch after about eight 
days. The young larvae feed in the same 
way as the adults, but it is the young 
which in feeding exude the reddish drops 
previously mentioned. In reaching full 
growth the larvae undergo two resting 
stages — prepupa and pupa, during which 
they take no food and remain motionless. 
Twenty to thirty days after the eggs have 
hatched the adult is ready for reproduc- 
tion (figs. ioa to c). 



DISEASES IN GREENHOUSE 131 






FIG. 20. GREENHOUSE ThripS, a EGG. & LARVA FIRST 
STAGE. C LARVA FULL GROWN. (AFTER RUSSELL.) 

Besides the sweet pea, thrips feed on 
lilies, azaleas, croton, dahlia, phlox, ver- 
bena, pink, and ferns, and on a number of 
other ornamentals, both in the greenhouse 
and in the open. 

RED SPIDER 

Tetranckys bimaculatus Harv. 

Even more dangerous to sweet peas than 
mites are Red Spiders (fig. 21), which at- 



132 DISEASES OF THE SWEET PEA 




FIG. 21. THE RED SPIDER, ENLARGED. (AFTER BANKS.) 

tack both leaves and stems, the method of 
attack and the resulting injury somewhat 
resembling that of mites. However, the 
spots caused by red spiders are reddish in- 
stead of a pale white. 

Life History. The adult female is usu- 
ally brick red in color and the male is red- 
dish amber. Frequently, however, the 
color of the red spider changes according to 
locality and food plants. The female lays 



DISEASES IN GREENHOUSE 133 

50 to 60 eggs, depositing about six per day 
for a period of nine days or so. The eggs 
hatch after about four days. After two 
days' activity, the young larva? pass into 




FIG. 22. TRIPHLEPS INSIDIOSUS, AN ENEMY OF THE RED 
SPIDER. (AFTER MCGREGOR.) 

the pupal or resting stage. The adults 
mate and the female is soon capable of 
laying. 

In the greenhouse the red spider mi- 
grates from the tomato and other plants to 
the sweet pea. The violet especially is a 



134 DISEASES OF THE SWEET PEA 

favorite host. Outdoors the red spider 
may attack sweet peas, tomatoes, wild and 
cultivated violets, beans, cowpeas, dahlia, 
Jamestown weed, wild blackberry, and 
the wild geranium. Although red spiders 
have few natural enemies, yet the insect 
Thriphleps insidiosus (fig. 22) frequently 
helps to keep it in check. 



CHAPTER V 

FIELD DISEASES OF SWEET PEAS 

As previously noticed, the diseases which 
affect sweet peas under glass may also be 
present out-of-doors. In fact the fungi 
such as Thielavia, Rhizoctonia, Fusarium, 
Sclerotinia, etc., are all known to induce, 
very commonly, diseases on plants in the 
held. Indeed their appearance in the 
greenhouse indicates their presence some- 
where in the field or in the manure pile, 
whence they are usually introduced into 
the soil. The spread of these fungous 
pests is favored by unnatural conditions 
which may occur in the field as well as in 
the greenhouse. Continuous foggy and 
damp hot weather, together with infected 

135 



136 DISEASES OF THE SWEET PEA 

soils, will naturally cause loss and disease. 
Thielavia root rot commonly found in the 
greenhouse produces a similar disease on 
sweet peas in the field. In the latter case 
it assumes greater economic importance, 
especially on trial grounds. Root knot 
has so far been encountered only on green- 
house sweet peas. It will doubtless be 
found in the field, however, before long. 
The same is also true for the Rhizoctonia 
root rot, the Fusarium root rot, and the 
Sclerotinia collar rot. Growers of sweet 
peas on a large scale for seed or for orna- 
mental purposes should be on their guard 
to prevent the introduction of these trou- 
bles into their soils. It is much easier to 
prevent infection than to eradicate a dis- 
ease that has once gained a strong foot- 
hold. Powdery mildew, a common leaf 
trouble in the greenhouse, is found also 
outdoors to some extent. On irrigated 



FIELD DISEASES 137 

sweet peas it assumes the nature of an epi- 
demic and may cause death of all the 
foliage. 

ANTHRACNOSE 

Glomerella rufomaculans (Berk.) V. Sck. 
and Sp. 

Of all field diseases Anthracnose is per- 
haps the most dreaded in the United 
States because of the great losses it occa- 
sions. Anthracnose on the sweet pea may 
exist wherever apples are suffering from 
bitter rot, for, as the writer has definitely 
proven, bitter rot of apples and anthrac- 
nose of sweet peas are caused by the same 
fungus, Glomerella rufomaculans. 

Symptoms. The symptoms of anthrac- 
nose are varied. Sometimes it is mani- 
fested by a wilting or dying of the tips 
(fig. 23) which become whitish and brittle 



138 DISEASES OF THE SWEET PEA 

and readily break off. At other times the 
injury extends further down and involves 
the entire branch. On the leaves the dis- 
ease starts as whitish spots, which enlarge 
until all the green gradually fades en- 
tirely, hence causing death (fig. 24) . 
Such infected leaves become brittle and 
soon drop off. Examination of an in- 
fected leaf with a hand lens shows that it 
is peppered with minute salmon colored 
pustules. At the time of blossoming the 
fungus also attacks the peduncle at the 
point of union with the buds, producing a 
bud blight; or the fungus attacks both the 
flower bud and the peduncle, in which case 
both dry up but do not fall off. The most 
easily distinguishable symptoms of this 
disease are on the seed pods. Infected 
pods lose their green color, become shriv- 
eled, and are soon covered with salmon 
colored patches which frequently attract 




Fig. 23. — Anthracnose Disease of Sweet Pea on stem 
and peduncles. 




Fig. 24. — Anthracnose Disease affecting Sweet 
Pea leaf. 



FIELD DISEASES 139 

attention. The disease is often worse 
where green Aphids are very active. In 
this case the older vines may be affected at 
any point. Very often, too, the harder 
vines may escape the disease which attacks 
the thin blades on each side. Here the af- 
fected blades become white and dry and 
break at handling. If not disturbed they 
become covered with pink pustules or 
fruits of the parasitic organism. 

The anthracnose, like the "streak," is of 
great economic importance. When once 
introduced into a field the disease spreads 
rapidly, often destroying the entire crop. 
Unlike "streak," the anthracnose may at- 
tack young seedlings, a condition some- 
times found in the greenhouse. In the 
field, the disease starts about July 1, when 
the plants are in full bloom and in the 
prime of beauty. This is also the time 
when the bitter rot disease of the apple 



140 DISEASES OF THE SWEET PEA 

(fig . 25) makes its appearance in the 
orchard. The fungus is carried over win- 
ter on cankered limbs and mummied fruits 
of diseased apples or on the diseased pods 
of the sweet pea as well as in the soil. 

Mode of Infection and Period of In- 
cubation. The anthracnose of the sweet 
pea is mainly a disease of the tender parts 
of the plant. Infection usually starts first 
at the tips, although, as previously shown, 
the fungus may attack the older parts of 
the plant once they have been injured by 
green Aphids or by red spiders. The 
spores of the parasite usually germinate in 
from six to twenty-four hours, according 
to the amount of moisture present. The 
germ tubes enter the host by breaking 
through the epidermal cells of either leaf 
or stem. 

The period of incubation varies from 
three to five days, according to the amount 





Fig. 25. — Bitter Rot of Apple induced by the same fungus 

which causes Anthracnose of the Sweet Pea, 

viz. Glomerella rufomaculans. 




Fig. 26. — Sweet Pea Mosaic, showing, a. leaflet 
affected with the disease, b. healthy. 



FIELD DISEASES 141 

of moisture in the atmosphere. The 
acervuli or spore pustules appear within 
five days after wilting begins, unless the 
weather is dry, when they may not appear 
until considerably later. 

MOSAIC DISEASE OF THE SWEET PEA 

Sweet Pea Mosaic is a serious disease. 
It greatly checks greenhouse peas and is 
equally injurious to sweet peas grown out- 
of-doors. Although the cause of the 
trouble is not as yet known, nevertheless 
all indications tend to show that it is in- 
duced by a definite pathogenic organism. 
The same or a similar mosaic is known to 
attack a number of plants such as tobacco, 
egg plant, pepper, tomatoes, and clovers. 
Its occurrence on the sweet pea has been re- 
corded only by the author ' though it has 

1 Taubenhaus, J. J., Present knowledge of sweet pea 
diseases. Florist Exchange 34: 108-110, 1912. 



142 DISEASES OF THE SWEET PEA 

probably been seen by a number of grow- 
ers. 

Symptoms. Mosaic is readily distin- 
guishable by a yellow dotting or mottling 
of the leaf, presenting in some instances 
a beautiful mosaic structure, whence its 
name (fig. 26) . Affected leaves linger for 
a time but they eventually lose all their 
chlorophyll and soon drop off. Another 
symptom of this disease is a curling of 
leaves (fig. 27) resembling the curling in- 
duced by the green Aphids, but in this 
case the insects have no association with 
it. The disease makes its appearance after 
the seedlings are from two to three weeks 
old. Often, the trouble is so serious and 
the curling so pronounced that the plants 
thus affected cannot make any headway 
and remain dwarfed. An attempt is made 
by these curled plants to produce a few 
flowers, but the latter are borne on very 




Fig. 27. — Mosaic Disease causing dwarfing 

of the plant and a rolling of the tip 

leaves. 



FIELD DISEASES 143 

short peduncles as compared with the long 
peduncles of healthy plants of the same va- 
riety. Frequently, however, the affected 
plants outgrow the disease entirely, and 
thus a distinct line of demarcation is ob- 
served between the previously diseased 
part and the healthy part of the new 
growth (fig. 28) . In rare cases, infected 
plants seem to thrive in spite of the dis- 
ease. Such plants should be selected for 
the purpose of breeding resistant strains. 
Pathogenicity. Like peach yellows 
and the mosaic disease of tobacco and 
tomato, mosaic of the sweet pea can be 
reproduced by puncturing with a sterile 
needle from the diseased leaf into a healthy 
one. As yet it has not been possible to 
find an organism associated with the dis- 
ease. Nevertheless the disease is conta- 
gious. It takes from ten to fifteen days for 
the disease to appear when artificial inocu- 



144 DISEASES OF THE SWEET PEA 

lation is carried out. The symptoms pro- 
duced in artificially inoculated plants are 
similar to those in the field. 

STREAK DISEASE 

Bacillus lathyri Manns and Taub. 

Streak is the only bacterial disease 
which affects this plant and no disease 
of the sweet pea is so little known to 
the growers. The attention of Professor 
Manns and the author was called to it 
in the course of our investigations, that 
is to say, only about three years ago. 
It probably has existed, however, a long 
time in this country, since it attacks so 
many other members of the legume family, 
the red clovers particularly, upon which 
it causes trouble of considerable economic 
importance. In England this disease is 
ruining the sweet pea crop every year. In 
this country it has gained a strong foothold 




Fig. 28. — Mosaic Disease, shewing where the 
plant has outgrown the trouble. 

x indicates the area where the disease has ceased 
activity. 



FIELD DISEASES 145 

and it is to be found wherever clovers are 
grown. 

Symptoms. Like the bacteriosis of the 
bean, streak makes its appearance in the 
season of heavy dew. On the sweet pea 
the disease usually appears just as the 
plants begin to bloom; it is manifested by 
light reddish brown to dark brown spots 
and streaks (the older almost purple) 
along the stems, having their origin usu- 
ally near the ground, which indicates dis- 
tribution by spattering rain and infection 
through the stomata or through insect in- 
jury. The disease becomes distributed 
quickly over the mature stems until the 
cambium and deeper tissues are destroyed 
in continuous areas, and the plant dies 
prematurely. From the stem the disease 
spreads to the petioles, flowers, peduncles, 
and pods, the symptoms in these cases be- 
ing similar to those on the stems. On the 



146 diseases of the sweet pea 

leaves, however, the disease appears as 
small circular spots, which gradually coal- 
esce and eventually involve the entire leaf, 
which when killed presents a dark brown- 
ish appearance. 

Pathogenicity. The pathogenicity of 
the causative organism may be proven by 
diluting a pure culture of the organism in 
sterile water and by spraying it on the 
healthy plants with an atomizer. This is 
done in the evening when the temperature 
is cooler and there is less chance for evapo- 
ration of the infectious liquid which is ap- 
plied. The disease makes its appearance 
from seven to ten days after artificial in- 
fection and the symptoms are similar to 
those produced in nature. The organism 
may be re-isolated from the artificially in- 
fected plants and the disease induced again 
at will on healthy plants, in each case the 
uninfected check plants remaining healthy. 



FIELD DISEASES 147 

Natural or artificial infection can only 
take place on mature plants which have 
started to bloom. All attempts to inocu- 
late plants in all stages of growth previous 
to the blooming period have failed. It 
seems that the host previous to blooming 
possesses certain protective properties 
which inhibit the growth of the parasite. 
The disease in the field does not make its 
appearance until the plants have started 
to bloom. 

Over 1,500 plate cultures of incipient or 
young lesions were made from the sweet 
pea and clover. The organism may almost 
invariably be taken in pure cultures from 
the young lesions in the stems of sweet 
peas when the surface is properly steril- 
ized. The parasite is a yellow organism 
which will grow luxuriantly upon any 
nutrient media containing sugars. On 
standard nutrient glucose agar the colonies 



148 DISEASES OF THE SWEET PEA 

appear within 24 to 36 hours. The center 
becomes granular and the colonies have a 
marked tendency to become stellate or au- 
riculate (fig. 29) . 

Morphological studies show the organ- 
ism to be a comparatively small rod-shaped 
bacillus, which in fresh cultures is rarely 
found in chains, and seldom united in twos 
or fours. The flagella or appendages of 
the organism are not easily demonstrated ; 
they are shed so readily that usually not 
more than two to five may be found in 
stained material and these are generally 
quite short. However, when the proper 
material is selected, carefully fixed and 
stained, the flagella may be demonstrated 
to be very long and delicate, and to be 
from 8 to 12 in number and well dis- 
tributed peritrichially. 




Fig. 29. — Pure culture of the streak 
organism, Bacillus lathy ri. 




Fig. 30. — Sweet Pea aphis parasitized by a fungus, 
Empusa aphidis. 



CHAPTER VI 

DISEASES NOT YET KNOWN TO ATTACK 
SWEET PEAS IN AMERICA 

In an article in the Sweet Pea Annual, 
Massee l describes a pea blight and a pea 
spot, which as far as is known have not 
yet made their appearance in this country. 

PEA BLIGHT 

Peronospora trifoliorum DeBy. 

According to Massee, this disease is very 
destructive to peas, lupines, and most 
other plants of the pea family. The dis- 
ease may appear and spread quickly when 
the plants are only a few inches high, or 
it may attack older plants. In dry 

1 Massee, G., Fungoid diseases of the sweet pea. 
Sweet Pea Annual, pp. 20-21, 1906, London. 

149 



150 DISEASES OF THE SWEET PEA 

weather the mycelium of the fungus 
spreads in the tissue throughout the leaf, 
which soon assumes a sickly yellow-green 
color, and finally bleaches, shrivels, and 
dies without showing any or only a small 
amount of the mold on the surface. In 
damp cloudy weather infected leaves show 
yellow patches, which soon become covered 
on one or both surfaces with a very delicate 
grayish lilac colored mold. 

The summer spores are produced on the 
leaves or on any other part of the host. 
The winter or resting spores are imbedded 
in the tissue of the host that has been pre- 
viously killed by the fungus. The resting 
spores have a very thick smooth brown 
wall. 

Peronospora vicicz also produces a dis- 
ease on sweet peas. 



DISEASES NOT YET KNOWN 151 

PEA SPOT 

Ascochyta pisi Lib. 

According to Massee, this disease attacks 
sweet peas, French beans and several other 
leguminous crops. The first indications of 
disease is the appearance on the pods of 
pale green spots of variable size and irreg- 
ular shape. These blotches continue to in- 
crease in size for some time and eventually 
become whitish, bordered with a dark line, 
and the surface is studded with minute 
black points which are the pycnidia or spore 
sacks of the fungus. 

It should be remembered that both Asco- 
chyta pisi and Peronospora trifoliorum are 
fungi very prevalent on other hosts in this 
country. It is only a matter of time until 
these parasites will be found to attack 
sweet peas. Growers, therefore, should be 
on their guard against these two troubles. 



CHAPTER VII 

INSECT PESTS 
THE SWEET PEA APHIS 

Macrosiphum pisi Kalt. 

Of all the sweet pea insects, not one 
perhaps rivals in economic importance the 
green aphis. Specimens were submitted 
to Professor Chittenden of the United 
States Department of Agriculture, who 
identified them as M. pisi Kalt. Since 
this pest is the same which also attacks the 
garden and field pea we will quote in part 
Professor Chittenden. 1 

Description. "The pea aphis is one of 
unusual size among those found infesting 

1 Chittenden, F. H., The pea aphis (Macrosiphum 
pisi Kalt.) U. S. Dept. Agr. Bur. of Entomol. Circ. 43 
Second Edition, 1909. 

*52 



INSECT PESTS 153 

gardens, and the largest of the green 
species which attacks the pea and related 
plants (fig. 31 atoe). The general color 




FIG. 31. SWEET PEA AphlS, a WINGED FEMALE. 6 SAME 
FROM SIDE WITH WINGS FOLDED IN NATURAL POSITION, 
AS WHEN FEEDING. C ApteTOUS FEMALE. d NYMPH 
IN LAST STAGE. ( AFTER CHITTENDEN.) 

of the insect is uniform pea green, the same 
color as the insect's favorite food plant. 
The eyes are prominent and reddish brown 
in color. The antennae are lighter than the 
body and the tubercules prominent. The 
legs are long and conspicuous. 



154 DISEASES OF THE SWEET PEA 

"Like the gipsy moth, the pea aphis seems 
to have been present in this country for 
about twenty-five years before it became a 
pest. It is now found practically wher- 
ever the garden pea and the sweet pea are 
grown, causing much injury to both hosts. 

"The reasons why the species has be- 
come so troublesome a pest are many: 
First, because of its ravages to a crop hith- 
erto little troubled by insects except the 
pea weevil, which has always been present 
in gardens and fields and has come to be 
looked upon as a necessary evil. Second, 
it is a species never before noticed so far 
as records go as having been destructive to 
peas of any kind in this country. Third, 
because of the great difficulty in keeping it 
in check. 

"Although garden and field peas are the 
crops most injured by this pest, sweet peas 
and red and crimson clover, as well as 



INSECT PESTS 155 

vetches, are affected. Attacks begin on 
the young pea vines; the 'lice' gather in 
clusters at first under and within the termi- 
nals, and as the leaves become covered they 
attack also the stems and by their numbers 
and veracity sap the life of the plant. 
Whole areas of vines are seen covered with 
the aphis." 

How the Aphids Multiply. The 
"lice" spend the winter in the egg stage. 
When the young sweet pea seedlings ap- 
pear in the spring the lice hatch from the 
eggs, and instead of being partly males 
and partly females, all are females, known 
as stem mothers. These without the in- 
tervention of the male give birth to a sec- 
ond generation, all of which are likewise 
females. These females in turn give birth 
to a third generation of females and in this 
manner a large number of successive gen- 
erations are produced, in none of which 



156 DISEASES OF THE SWEET PEA 




FIG. 32. SHOWING HOW APHIDS FEED AND THE NECESSITY 
OF A CONTACT SPRAY TO KEEP IT IN CHECK. (COURTESY 
OF THE KENTUCKY TOBACCO PRODUCTS CO.) 

do any males occur. This form of repro- 
duction without the intervention of the 
male is known as parthenogenesis. On the 
approach of cool fall weather a generation 



INSECT PESTS 157 

composed of both males and females are 
produced, the sexes mate, and eggs are 
laid which pass the winter on dead stems 
or in the ground. According to present 
knowledge the eggs hibernate on clover or 
vetch. The sweet pea aphis derives its 
food by sucking on the plant juices (fig. 

32). 

The sweet pea aphis is not only a pest 
by itself, but it also aids in carrying the 
virus of mosaic from plant to plant. 
Moreover, plants which have their juices 
constantly depleted by numerous sucking 
aphids are thereby weakened and easily 
fall the prey to diseases, especially streak 
and anthracnose. If the green aphis could 
be successfully controlled, nearly 80 per 
cent of the other troubles would be pre- 
vented from getting a start. 

Greenhouse sweet peas are not exempt 
from the attacks of the aphis. In the 



158 DISEASES OF THE SWEET PEA 

greenhouse, too, the prevalence of the aphis 
is always correlated with an abundance of 
mosaic, as well as with weak spindly 
plants. 

The sweet pea aphis is very prolific. It 
is estimated that each individual if al- 
lowed full sway would be the progenitor 
of 423,912 aphids in one season. These 
lice, however, are fortunately kept in check 
by natural enemies. The list of insects 
known to feed on the sweet pea aphid 
includes seven species of lady beetles, three 
species of Syrphus or lace wing fly, a sol- 
dier beetle, and a few minute four winged 
Hymenopterous parasites. 

Lady Beetles. Hippodamia converg- 
ens. It behooves every grower to learn to 
recognize this friendly insect. Its eggs 
are laid in clusters, found everywhere on 
board fences or on trees. The eggs are 
small, salmon color, and pointed at both 



INSECT PESTS 159 

ends. The larvae as they emerge from the 
eggs soon begin to feed on very small in- 
sects. Their body is long, very rough, 
hairy, and dark with red or yellow mark- 
ings on its back. As soon as they reach 
maturity they attach themselves by the 
tail end to some twig and there pupate. 
From this stage emerges the adult lady 
beetle. The sexes mate and the females 
lay the eggs which are to begin a new life 
cycle (fig. 33 a to c ) . 




FIG. 33. THE CONVERGENT LADY BEETLE (Hippod(Wlia COfl- 

vergens) an enemy of the sweet pea aphis, a 

ADULT BEETLE. b PUPA. C LARVA. (AFTER CHITTEN- 
DEN.) 



160 DISEASES OF THE SWEET PEA 

Syrphid Flies. Syrphus ribesii. In 
company with the plant lice are seen 
greenish, flat sticky looking "worms," 




fig. 34. syrphid fly, Syrphus Americanus, whose larva 

FEEDS ON THE SPRING GREEN APHIS AND ALSO ON THE 
SWEET PEA APHIS, O FEMALE FLY. b SECOND ABDOM- 
INAL SEGMENT OF MALE. (AFTER WEBSTER AND PHIL- 
IPS.) 

which are pointed at one end and seem 
to have no distinct head, eyes, or legs. 
These are larvae or maggots of a two- 
winged fly commonly known as Syrphid 
or Flower Fly. The maggots obtain 
their food by puncturing the body wall of 



INSECT PESTS 161 

the aphid and by sucking out its con- 
tent. When the maggot is full grown 
it seeks some sheltered spot where it 
pupates and becomes transformed into the 
adult fly. The adults are dark, with 
transverse yellow bands across the abdo- 
men (fig. 34 a and b) . They are swift 
fliers and are often mistaken for bees. 
They feed on the nectar of flowers and be- 
cause of this habit are often called Flower 
or Honey Flies. On hot days they are 
very numerous and are called Sweat Flies. 
They lay their eggs on vines attacked by 
the aphids. 

Green Lace Wing. Chrysopa calif or- 
nica. This insect is called Aphis Lion be- 
cause of its destructiveness to all green 
plant lice. The larvae of these beneficial 
flies are provided with two long curved 
mandibles upon which the aphids are held 
prisoners until they are sucked dry. They 



162 DISEASES OF THE SWEET PEA 




FIG. 35. GREEN LACE FLY (ChrySOpha OCltlatd) AN ENEMY 
OF THE SWEET PEA APHIS, O EGGS. b FULL GROWN 
LARVA. C FOOT OF SAME. d LARVA DEVOURING AN 
INSECT. € COCOON. / ADULT INSECT, g HEAD OF SAME. 
h ADULT NATURAL SIZE. (AFTER MARLATT.) 



are then released and others caught and 
destroyed in a similar way (fig. 35 a to h) . 
Aphiduis. Of still greater importance in 
the natural control of the sweet pea aphis, 
is the parasite known as Aphiduis testa- 
ceipes (fig. 36) . The adult female of this 
fly possesses a long sharp pointed ovipos- 
itor which pierces the body wall of the 



INSECT PESTS 



163 



louse depositing her eggs within its tissue. 
When the female Aphiduis comes in con- 
tact with an aphis, she quickly thrusts her 
abdomen beneath its thorax and head, giv- 
ing the aphis a quick stab, and deposits her 




fig. 36. Aphiduis testaceipes ovipositing in the body of 

AN APHIS. ENLARGED. ( AFTER WEBSTER.) 

eggs in its body. After being stung by her 
enemy, the aphis kicks up the posterior 
part of the abdomen as though in pain. 
It is probable that only one egg is depos- 
ited within the body of each attacked aphid. 
The egg upon hatching gives birth to a 
small legless larva which begins at once to 
feed upon the interior vital parts of the 
louse. The latter soon becomes less active, 



164 DISEASES OF THE SWEET PEA 

loses its natural color, then turns gray and 
dies, remaining attached to the part of the 
plant upon which it has been feeding. 
When the larva is fully developed it 
pupates and cuts a circular hole on the 
top of the body of the now "mummied" 
aphis, emerging as a winged insect to at- 
tack other living aphids in the same way 
as its mother. The circular hole cut by 
the escaped parasites is always a sure sign 
of the presence of these beneficial in- 
sects. 

In the summer of 1911, the author no- 
ticed that Aphiduis testaceipes alone de- 
stroyed and kept in check what seemed an 
epidemic of the sweet pea aphis. On the 
other hand, in the summer season of 1912, 
this beneficial parasite was rather scarce. 
It is, therefore, interesting to know the con- 
ditions which determine its presence or 
absence. The following are observations 



INSECT PESTS 165 

recorded by Webster and Philips : l The 
dispersion of Aphiduis may be accom- 
plished by the larvse in the bodies of the 
winged aphids whence it is carried from 
place to place and also by the wind. 
While the young larvse are within the 
body of the aphis they are not easily de- 
tected. It is only when the larva becomes 
nearly full grown that it may be detected, 
and then only by an expert observer. 
There may be millions of larvae of Aphiduis 
in a field and yet present no visible indi- 
cation of their presence. A few warm days 
bring about their final development, 
whereupon the presence of the leathery 
brown bodies of the parasitized aphids be- 
gin to attract the attention. Climatic con- 
ditions are important factors in determin- 
ing the abundance of Aphiduis. 

1 Webster, F. M., and Philips, W. J., The spring grain 
aphis or "green bug." U. S. Dept. Agr. Bur. Entom. 
Bull. 110, 1912. 



i66 DISEASES OF THE SWEET PEA 

Aphelinus. Another insect which par- 
asitizes the sweet pea aphids is Aphelinus 
nigritus, a parasite also known to attack a 
number of other green plant lice (fig. 37) . 




fig. 37. Aphelinus Nigritus; a parasite of the sweet 

PEA Aphis. (AFTER WEBSTER AND PHILIPS.) 

This insect, however, is not so active as 
the Aphiduis previously mentioned. 

Fungous Pests. The fungi which help 
to destroy the sweet pea aphids are not 
as yet well known. Empusa aphidis (fig. 
30) is the only fungus which has received 
some attention and study. The others re- 



INSECT PESTS 167 

main to be investigated. The develop- 
ment of Empusa aphidis depends upon 
rather warm, humid weather for its spread 
and is retarded by drought. This fungus 
was found fairly active during the sum- 
mer of 1912. It is possible to cultivate 
the fungus artificially and it may be used 
to inoculate broadcast the aphids in the 
field. 

THE TWELVE-SPOTTED CUCUMBER BEETLE 

Diabrotica 12 punctata Oliv. 

The larva of this insect feeds on roots 
and stalks of corn and on a number of 
other plants but as far as is known does not 
feed on roots and stems of sweet peas. It 
is the adult beetle of this insect that is 
troublesome to outdoor sweet peas. The 
beetle is one of the earliest pests seen to 
feed on the plants, as soon indeed as they 
are no more than six inches high. The in- 



168 DISEASES OF THE SWEET PEA 

jury is confined to the leaves, where it ex- 
tends over large areas. The beetle is often 
known as the 12 spotted cucumber beetle, 
the color of its body being yellowish green 
and its wing covers marked by twelve 
black dots. Besides the sweet pea, the 
adult beetle also feeds on cucumber, 
squash, and melon blossoms. It also feeds 
on alfalfa, clover, cotton, rye, and to- 
bacco. This species is abundant in the 
Southern states; although its range in the 
North is also very wide. Despite its being 
an early species, the beetle is also found 
feeding on sweet peas which have long 
passed blooming. 

The Blister Beetles. Epicauta sps. 
Blister beetles feed on sweet pea plants 
from the beginning of the seedling stage 
up to maturity. Two species of blister 
beetles are troublesome to sweet peas ; the 
black and the striped. 



INSECT PESTS 169 

The Black Blister Beetle. Epzcauta 
pennsylvanica DeG. As the name implies, 
this bettle is uniformly black. It meas- 
ures a little over a quarter of an inch in 
length. It feeds on a wide range of plants 
such as the potato, tomato, cabbage, carrot, 
beet, corn, bean, aster, clematis, zinia, 
sweet pea, and a number of other ornamen- 
tals. In the absence of other food it is 
commonly found feeding on different rag- 
weeds (Ambrosia sp.), on golden rod, on 
amaranth, and on iron weed. This beetle, 
too, has a wide range of territory. 

The Striped Blister Beetle. Epi- 
cauta vittata Fab. This species is about 
half an inch in length with blackish wing 
covers, each of which is bordered with yel- 
low and has a yellow stripe down the cen- 
ter (fig. 38). It injures potatoes, toma- 
toes, beets and mangels, turnips, beans, 
peas, radishes, melons, corn, clover, alfalfa, 



170 DISEASES OF THE SWEET PEA 




FIG. 38. THE STRIPED BLISTER BEETLE. (AFTER CHITTEN- 
DEN.) 

and sweet peas. According to Professor 
Chittenden ' the beetle lays its eggs on 
plants or on the ground. From each egg 
hatches a small long-legged larva, which 
runs actively in search of a grasshopper 
egg pod which it enters and feeds upon. 
Afterwards it casts its skin several times 
and finally becomes transformed into a 
beetle. 

There are also a number of caterpillars 
which feed on the sweet pea, but they have 
as yet not been studied carefully. 

1 United States Department of Agriculture, Year 
Book, 1898. 



INSECT PESTS 



171 



SOIL INFESTING INSECTS 

Variegated Cutworms. Peridroma 
saucia. These are common garden pests 
attacking a number of other plants as 
well in addition to the sweet pea (fig. 
39 a to /) . Cutworms are troublesome 
the first year when sweet peas are planted 




FIG. 39. VARIEGATED CUT WORM, a MOTH. b LARVA 

FEEDING. C LARVA RESTING. d EGGS LAID ON DEAD 
TWIGS. e CLUSTER OF EGGS MAGNIFIED. (AFTER CHIT- 
TENDEN.) 



172 DISEASES OF THE SWEET PEA 

on old sod. They are sometimes intro- 
duced into a new place with the compost. 
The larvae of cut worms have the habit 
of cutting herbaceous plants at the stem 
end. The injury is inflicted at night or 
on dark days: the worms return to the 
ground as soon as the sun appears. The 
adult of the cutworm is a moth which 
lays her eggs in old fields or pastures where 
there is plenty of grass for the young larvae 
to feed upon. As the young hatch, they 
feed on roots of grass. The first season 
the young cutworms usually attain about 
half an inch in length. As winter ap- 
proaches they build earthen cells in the 
ground and thus protect themselves from 
cold weather. In the spring, if the field 
is allowed to remain in grass, plenty of 
food is on hand for them. However when 
the sod is plowed under, and other garden 
crops planted, such as the sweet pea, the 



INSECT PESTS 173 

natural food supply of the worms is cut 
off and they are compelled to feed on the 
cultivated plants. These are severely in- 
jured if the insects are abundant. 

Wireworms Melanotus communis are 
a prominent pest of field crops. They 
are the young of click beetles, also known 
as snapping bugs. Wire worms are brown 
hard bodied larvae of nearly uniform size 
throughout. They bore into various seeds 
after planting or work on the roots of 
various plants, often causing serious in- 
jury. The eggs are laid on old pasture 
land, and the larvae which hatch from them 
normally work on the roots of grasses. If 
the sod is replaced by any other cultivated 
crop, the larvae are forced to feed on that 
crop for want of its normal host plant. 
Sweet peas often suffer from this pest, 
although the injury is not apparent until 
they are in bloom. 



174 DISEASES OF THE SWEET PEA 

Differing from cut worms, wireworms 
pass from three to five years in the larvae 
stage; hence wireworms of different ages 
may be found in the same place feeding 
side by side. 

White Grubs. Lachno sterna sp. 
White grubs are the larvae of May beetles 
(fig. 40 a to /) . They are injurious to a 




FIG. 40. WHITE GRUB OR MAY BEETLE, a BEETLE. b 
PUPA. C FULL GROWN LARVA OR WHITE GRUB. (AFTER 
CHITTENDEN.) 

number of cultivated plants, the sweet pea 
being included. May beetles lay their 
eggs in sod, in corn fields, or in the garden. 
The grubs hatch about the middle of July 
and begin feeding on roots, growing 



INSECT PESTS 175 

slowly, and requiring two years or more 
to become full size. Larvae of proper age 
and size change to pupae in midsummer 
and the adult stage is reached by Septem- 
ber, but the beetles remain in the earthen 
cells made by the larvae until the following 
spring. Thus it is seen that the life cycle 
of white grubs is similar to that of wire- 
worms. Larvae of different ages are pres- 
ent in the soil at all times in the year; 
hence injury caused by them may be con- 
tinuous. 



CHAPTER VIII 

DISEASED SEEDS 

Anthracnose. Under the discussion 
of anthracnose we have already seen that 
disease may be transmitted with the seed. 
In that case infection starts on the pods 
and the disease works inwards, gradually 
penetrating the seed coat and the seed 
proper (fig. 41). Such seeds when har- 
vested have a shriveled appearance and 
when planted with healthy seeds introduce 
the trouble into the soil. 

Streak. Another disease that may be 
transmitted with the seeds is the "streak." 
In examining infected plants we can read- 
ily see that the disease has invaded the 

pods and the seeds within. When such 

176 




Fig. 41. — Anthracnose Disease of pods and seeds. 
The arrows shew the diseased spots. 



DISEASED SEEDS 177 

seeds are planted, they may introduce the 
parasite into the soil. 

Shriveled Seeds. Sweet pea seeds, as 
sold by seedsmen, as put up in small paper 
packages. In very few cases are all the 
seeds plump and full. A certain per cent 
are shriveled and give the appearance of be- 
ing diseased. Such seeds are not always 
diseased. These shriveled seeds often ger- 
minate as readily as the plump ones, and as 
they swell cannot be told from others. It 
seems that the shriveling is correlated with 
loss of water, and this seems to be charac- 
teristic of some varieties more than of 
others. However, it is difficult to tell 
whether such seeds in the long run produce 
weaker plants which are more susceptible 
to disease. A small percentage of the 
shriveled seeds fail to germinate. Some 
of these no doubt are hard seeds which can- 
not germinate because of their impervious 



178 DISEASES OF THE SWEET PEA 

seed coats. Others upon culturing in the 
laboratory are found to contain a variety 
of fungi, such as Alternaria, Fusarium, 
Clonostachys, Rhizopus, and Botrytis (fig. 
42) . These seem to play the role of sap- 
rophytes on the growing plants, but they 
may be weak parasites, capable of attack- 
ing these few shriveled seeds which may 
lack in vigor and resistance. 

The Drug Store Beetle. 1 Sitodrepa 
panicea. This minute beetle (fig. 44) 
is of considerable economic importance 
to seedsmen, since sweet pea seeds in the 
storehouse are very frequently seriously 
injured by it. This pest is often found 
feeding on dry bread, and because of 
this, it is known in Europe as the bread 
beetle. In this country it is found to 

1 See also Bull. 4. Bur. Entom. U. S. Dept. Agr., 
1896. 





** 


^ 


■a 


& 




^ 




*4 




•a 





*k 



Fig. 42.— To the left, Fusarium and Botrytis fungi from 
shriveled and non-germinated Sweet Pea seeds; 
to the right, shriveled seed soaked 3 minutes in a 
2% formaldehyde solution. 



DISEASED SEEDS 179 

be a very common pest in drug stores, 
whence its name. It also invades mills, 
granaries, and warehouses of all kinds. 
It also invades the kitchen where it feeds 
on red pepper, flour, and all sorts of 
breakfast foods. It also eats ginger, 
rhubarb, chocolate, dried fruits, beans, 
peas, coffee, rice, and other seeds of every 
description. Its larva is often found as a 
book worm. The larva of this beetle is 
so voracious that it is said to "eat anything 
except cast iron." It is also the larva of 
this beetle that is so fond of sweet pea 
seeds, tunneling the inside, and thus com- 
pletely destroying the germinating power 
of the seed. The adult beetles mate and 
the female lays her eggs on sweet pea seeds 
and elsewhere. The young upon hatching 
at once begin to tunnel into the seeds. In 
the storehouse there are usually four broods 



180 DISEASES OF THE SWEET PEA 

formed during the winter and if allowed 
free range may destroy large quantities of 
seed. 

Seedsmen whose storehouses are serious- 
ly infested with these pests will find relief 
by the use of bisulphide of carbon evapo- 
rated at the rate of one pound of the chem- 
ical to each 1,000 feet of cubic space. 
While fumigating, the room should be 
closed tightly and care taken to keep away 
lighted cigars, matches, or burning candles. 




Fig. 43. — Auto Spray 
No. 1. 

Courtesy of E. C. Brown Co., 
Rochester, N. Y. 




Fig. 44. — The Drug-store Beetle, an enemy to stored 
Sweet Pea seeds. 



CHAPTER IX 

PHYSIOLOGICAL DISEASES 

Physiological diseases are those dis- 
turbances of the normal activity of a plant 
which are not induced by fungi, bacteria, 
or insects. 

Bud Drop. The young flower buds at a 
very early age, turns yellow and drops off. 
This disease is sometimes confused with 
the drop produced by the anthracnose dis- 
ease. In the latter case the flower develops 
into a normal spike, but it is attacked soon 
by the fungus, Glomerella rufomaculans, 
which girdles it at the point of attachment 
between the flower and the peduncle. In 
this case the blossom falls off, leaving be- 
hind the beheaded peduncle. In bud drop, 

181 



182 DISEASES OF THE SWEET PEA 

however, the minute young blossoms fail 
to develop, and drop off while very young. 

This form of drop is attributed to an 
unbalanced condition of food elements in 
the soil. This may occur in a soil that has 
been excessively fed or in a soil that is 
lacking in plant food. Bud drop has ac- 
tually been found in the laboratory on 
sweet pea plants grown in pots which re- 
ceived heavy applications of manure, and 
in pots filled with a very poor clay soil. 
The trouble has been overcome by the ap- 
plication of 150 lb. of muriate of potash 
and 600 lb. of acid phosphate per acre. 
As a result of this treatment the drop 
ceased within a week, and a luxuriant crop 
of flowers was produced. An application 
of a balanced fertilizer to the pots above 
mentioned readily helped the plants to 
overcome the drop. 

Root Burn. This trouble, probably, is 



PHYSIOLOGICAL DISEASES 183 

a physiological disease. It is induced by 
the excessive use of fertilizers. The fol- 
lowing facts from the letter of a grower 
who wrestled with this trouble will help to 
confirm the belief in the physiological 
nature of this disease: "The seeds were 
sown November 1 in pots and planted De- 
cember 15 in the beds in the greenhouse. 
Previous to the planting, the beds were 
well manured with horse manure, which 
was applied six months before planting. 
Besides this, wood ashes were also applied 
at the rate of 1,500 lb. to 4,500 square feet 
of bed space. This would be equivalent 
to nearly seven and one-half tons per acre. 
About one month after planting, some of 
the plants turned yellow and died; others 
remained dwarfed and offered a languid 
appearance." Upon examining some of 
the plants, they were found to be dwarfed 
and to have a sickly yellowish look. The 



184 DISEASES OF THE SWEET PEA 

roots were dwarfed, blackened as though 
burned, resembling the injury of Thielavia 
root rot. Upon testing the soil it was 
found to be strongly alkaline. Hard wood 
ashes, contain about 30 per cent caustic 
lime and from 5 to 12 per cent potash. It 
was the excess of both of these substances 
that made the soil so alkaline, the roots of 
the sweet peas becoming burned and inhib- 
iting growth. This kind of injury could 
be considered purely physical ; nevertheless 
any injury which interferes with the nor- 
mal functions of the parts of the plants 
also results in a disturbance in its metabol- 
ism, and is therefore considered as a physio- 
logical trouble. A remedy for this was 
found in the use of acid phosphate, fol- 
lowed by a good drenching of water. This 
helped to neutralize the alkalinity and to 
balance the food rations in the soil. 



CHAPTER X 

METHODS OF CONTROL 

Growers who expect to find in these 
pages a "cure all" for their sweet pea trou- 
bles will be disappointed. Once a tender 
sweet pea plant is invaded by fungi or bac- 
teria it can rarely be cured. Insects, how- 
ever, may be destroyed, since it is possible 
to poison them, although the task is often 
difficult because they are not easily ac- 
cessible. 

The problem, therefore, is one of pre- 
vention. Sweet pea growers would win 
ninety per cent of the battle if they would 
realize the importance of preventive meth- 
ods. Here, as elsewhere, the old dictum 

holds true, "an ounce of prevention is 

185 



186 DISEASES OF THE SWEET PEA 

worth a pound of cure." Yet even here, 
the personal element is the determining 
factor in success. Growers too often work 
by "rule o' thumb." Some have their pet 
theories as to causes of disease ; others have 
their remedies, favorite fungicides in- 
tended to act as a cure all but which do not 
often yield the promised results. Progres- 
sive growers find it profitable to keep in 
close touch with Plant Pathologists in the 
various Experiment Stations. More than 
this, every grower should develop the 
power of keen observation, for plant dis- 
eases are too often not detected until too 
late. 

RESISTANT VARIETIES 

The most promising means of control is 
the use of resistant varieties. It is true 
that resistant varieties will encourage the 
lazy man to neglect his seed, disregard ro- 
tation, and overlook all sanitary methods ; 



METHODS OF CONTROL 187 

nevertheless, resistant varieties are often 
the only protection against complete an- 
nihilation of a species by disease. In pass- 
ing through a sick field, one cannot help 
but notice that not all the plants of the 
same kind are subject alike in the same 
way to the disease. Some are killed out- 
right ; others are partly affected, or if badly 
affected, resist the disease; and still others 
are not at all diseased. If, therefore, we 
are able to select the seed from the resistant 
strain and multiply it rapidly, we will ob- 
tain resistant plants capable of producing 
100 per cent healthy plants in a sick soil. 
That this is possible there can be no doubt. 
A strain of cowpeas has been obtained 
which is resistant to wilt, and a strain of 
clover has also been obtained which is re- 
sistant to anthracnose. Of course, it can- 
not be expected that a strain will be re- 
sistant to every disease, but there is no 



188 DISEASES OF THE SWEET PEA 

doubt that we may obtain strains resistant 
to more than one disease. 

SEED TREATMENT 

It was previously shown that the seeds 
are capable of carrying anthracnose and 
possibly also the streak disease. It is 
therefore unwise to plant sweet pea seeds 
without first treating them. Heating the 
seed in hot water at various temperatures 
of 100 degrees, 90, 80, 70 and 60 de- 
grees C. from one second to five minutes 
does not seem to yield promising results. 
Soaking the seed in sulphuric acid from 
five to fifteen minutes helps to accelerate 
germination, especially of the hard seed; 
and it also destroys all harmful germs 
which adhere to the seed coat. After soak- 
ing the seeds in the sulphuric acid, they 
should be thoroughly washed in running 
water, then dried and planted in the usual 



METHODS OF CONTROL 189 

way. Treating the seed with the acid for 
one hour will greatly reduce its percentage 
of germination, and by prolonging the 
treatment to one and a half hours, germina- 
tion will be inhibited altogether. 

Soaking the seed in a solution of one 
pint of formaldehyde in 30 gallons of 
water for ten minutes will also destroy 
spores which adhere to the seed coat. The 
formaldehyde treatment however does not 
seem to help the germination of the seed. 
It should not be expected that the seed 
treatment will remove all evils. It is only 
beneficial in that it kills all spores of 
parasitic fungi which may adhere to the 
seed coat. Seeds which are diseased and 
which have their interior tissue invaded by 
parasitic organisms will not be benefited 
by the treatment, since the chemical cannot 
penetrate the seed to reach the interior 
lodging parasite. The use and selection 



igo DISEASES OF THE SWEET PEA 

of clean, healthy, plump seeds is as im- 
portant as the seed treatment. 

CONTROL OF SICK SOILS 

The habit of many growers of sweet 
peas is to use the same soil in the beds for 
a period of years. It is even claimed that 
this practice tends to produce stronger 
vines. This may be true as long as the soil 
remains uninfected. However, no sooner 
does contamination set in with either Rhi- 
zoctonia, Fusarium, Thielavia, Chaetom- 
ium, or the eel worm, than it becomes diffi- 
cult, if not impossible, to obtain a stand of 
sweet peas. The remedy of course is to 
throw out the old soil and bring in fresh 
dirt free from disease. This unfortunate- 
ly is not always a safe method, for the rea- 
son that the new soil too may be contami- 
nated, or that it may readily become in- 
fected as soon as it is placed in the 




Fig- 45- — Soil infected with Fusarium lathyri, the cause 
of Sweet Pea Wilt : a. the soil was steam-sterilized, 
resulting in a perfect stand; b. check unsterilized. 
The seedlings in both pots are of the same age. 



METHODS OF CONTROL 191 

previously contaminated bed. Infected 
greenhouse soil may be rendered useful 
and free from disease by either the steam 
or the formaldehyde methods of steriliza- 
tion. 

(a) Steam Sterilization. This method 
is practical in the greenhouse (fig. 45) 
or on seed beds only where the areas are 
limited. Its use is possible only where 
steam is to be had from a boiler capable 
of producing from 80 to 90 lb. pressure. 
The method of sterilization is as follows : 
before planting, prepare the soil in the 
regular way, adding the necessary amount 
of manure and fertilizers. At the bottom 
of the bed or bench, pipes or drain tiles are 
laid parallel to each other two feet apart. 
The pipes are perforated with 1-6-inch 
holes throughout. These pipes or tiles are 
closed at the farthest end so that the steam 
may come out through the cracks or holes. 



192 DISEASES OF THE SWEET PEA 

The other end of the tiles or pipes fits into 
a cross-pipe which is connected with the 
main steam pipe in the boiler. The steam 
is now turned on and as fast as it escapes 
from the holes it penetrates and heats the 
soil in the bench or bed. The steam is 
turned on from one to two hours according 
to the constancy and strength of the pres- 
sure. A good method of determining when 
to turn off the steam is to bury a few raw 
potatoes at the surface of the bed and cover 
them with some straw or sacking. When 
the potatoes are cooked the sterilization 
has been completed. This method of ster- 
ilization has the advantage of killing the 
eel worm and all the other soil troubles as 
well as the weeds. As above described, it 
is somewhat expensive in the initial cost of 
installation. But once put in, it serves a 
number of years, and the pipings too may 



METHODS OF CONTROL 193 

be used for sub-irrigation, a very desirable 
method of watering the beds. 

A cheaper method of steam sterilization 
is the "inverted pan method," which may 
also be used to sterilize seed beds and 
frames outdoors. The method has given 
excellent results and because of its sim- 
plicity and small cost is recommended 
for use in large or small areas. It is the 
invention of Mr. A. D. Shamel of the 
United States Department of Agricul- 
ture. The apparatus consists ®f a gal- 
vanized iron pan 6 ft. by 10 ft. and 6 in. 
deep, which is inverted over the soil to 
be sterilized, and steam is admitted under 
pressure. The pan is supplied with steam 
hose connections, has sharp edges which 
are forced into the soil on all sides to pre- 
vent the escape of steam, and is fitted with 
handles for moving it from place to place, 



194 DISEASES OF THE SWEET PEA 

the weight of the entire pan not being over 
400 lb. The soil to be sterilized is pre- 
pared as in the previous method, a few 
potatoes being buried to gauge the amount 
of heat produced. The steam is kept at 
as high a pressure as possible, 80 to 100 
lb. being best, for one to two hours accord- 
ing to the pressure maintained. When 
one section of the bed is treated, the pan 
is lifted and carried to an unsterilized por- 
tion and the operation is repeated until the 
entire bed is steamed. 

(b) Formaldehyde. When steam ster- 
ilization is not feasible because of the 
absence of a steam boiler or for some other 
reason, the formaldehyde treatment is the 
next best. It will kill Thielavia, Fusar- 
ium, Rhizoctonia, Pithyium, and Chaeto- 
mium in infected soils. It is doubtful, 
however, if it will entirely remove eel 
worms from such soils. The formalde- 



METHODS OF CONTROL 195 

hyde method is applied as follows: 
The beds are thoroughly prepared in the 
same way as in other methods of steriliza- 
tion and are drenched with a formalin solu- 
tion composed of one pint of commercial 
formaldehyde to 25 gallons of water, one 
gallon of this solution being used to each 
square foot of bed space. The solution 
should be put on with a watering can and 
distributed as evenly as possible over the 
bed so as to wet the soil thoroughly to the 
depth of a foot. It will in most cases be 
necessary to apply this solution two or 
three times, as the soil will not absorb this 
quantity of liquid at one time. After the 
treatment the beds should be covered with 
heavy burlap to keep in the fumes for a 
day or so, and then aired for a week before 
planting. Stirring the soil at this time 
helps the escape of the formaldehyde 
fumes. 



196 DISEASES OF THE SWEET PEA 

(c) Infected Areas. In the green- 
house, damping off or any other of the soil 
troubles usually starts at one part in the 
bed and from there spreads all over the 
bed. Where only a few of these centers of 
infection occur, much damage may be pre- 
vented by immediately removing the in- 
fected plants and soil from the bed to- 
gether with the surrounding area somewhat 
beyond the last signs of disease. 

(d) Cultural Considerations. Every 
factor which leads to a weakening of the 
plants should be eliminated. In the green- 
house, overfeeding as well as underfeed- 
ing, overwatering, and excessive high tem- 
peratures with lack of ventilation should 
be avoided. 

(e) Other Preventive Methods in 
the Greenhouse. Usually the soil in 
the greenhouse is infected with manure, 
with potted plants started early in a cold 



METHODS OF CONTROL 197 

frame, or with diseased tomatoes, the 
violets, and a number of other hosts grown 
as alternating crops. It goes without say- 
ing that the grower should not knowingly 
bring in sick soil into the greenhouse, nor 
should a sick soil from indoors be dumped 
in the open where sweet peas or any other 
crops are likely to be grown for ornamental 
or commercial use. Care should be taken 
to allow no access to diseased violets or 
diseased plants of any kind. 

CONTROL OF OUTDOOR SICK SOILS 

Unlike greenhouse soils, affected areas 
outdoors are not so easily treated. In a 
small garden plot, as in the home garden 
for instance, a sick soil may be sterilized 
either with steam, using the inverted pan 
method, or with formaldehyde, as in the 
case of the greenhouse. Where sweet peas 
are grown on a large scale, as for seed pur- 



198 DISEASES OF THE SWEET PEA 

poses, the problem of handling sick soils 
becomes a more difficult matter. In this 
case neither the formaldehyde nor the 
steam methods are applicable, since either 
is too expensive when used on a large scale 
and hence is not practical. There are, 
however, other control measures which may 
prove helpful. 

(a) Cleanliness. It is a common prac- 
tice to allow sweet pea plants which have 
passed their usefulness to winter over in 
the field. As spring comes, the dead vines 
are plowed under. In cases of fall plow- 
ing and sowing the old vines are immedi- 
ately turned under. Should these vines 
have suffered from disease the previous 
season, they would at once re-infect the soil. 
As time goes on the land may become so 
contaminated as to be unfit for sweet peas 
for a number of years. To obviate this 
the old vines should be burned as soon as 



METHODS OF CONTROL 199 

they pass all usefulness and as soon as they 
have sufficiently dried. The expense and 
the labor of this operation should not in- 
fluence the grower to neglect this. This is 
especially true for the seedsman whose 
success depends largely on clean lands in 
order to produce clean seed which will 
meet the market requirements. 

(b) Manure. Florists and growers 
often dump potted plants on the manure 
pile or on the compost. Such plants may 
often be infected with some of the soil 
troubles to which the sweet pea is sus- 
ceptible. The use of such infected manure 
or compost may mean the ruin of an entire 
field. To avoid outdoor contamination of 
our sweet pea soils, extreme care must be 
taken that no contaminated manure or 
compost find its way into the plantations, 
(c) Crop Rotation. This is an essen- 
tial and effective means of controlling soil 



200 DISEASES OF THE SWEET PEA 

sickness. With this system the parasite is 
starved out for lack of the proper hosts. 
With the sweet pea, the selection of hosts 
for proper rotation is a difficult one. So 
many of the cultivated and ornamental 
plants, for instance, are subject to the root 
rots which also attack sweet peas. The 
safest method, perhaps, for seed grow- 
ers, would be to have sweet peas alternated 
every second or third year with a cereal 
such as sweet corn, sugar cane, or millet. 
Where soils are already badly affected, 
sweet peas should be grown on the same 
land every fifth or sixth year. 

(d) Fertilizers. Outdoor sweet peas 
are not as yet known to suffer from eel 
worm attacks. However, should this oc- 
cur, increase of fertilizer will undoubtedly 
prove to be a good method of handling 
root knot by forcing the growth of the root 



METHODS OF CONTROL 201 

system. Observations show that nema- 
tode injury is confined to the upper roots 
of the plant, that is, those which are 12 to 
16 inches deep. Hence, if the roots are 
induced to penetrate deeper in the soil, 
part of the injurious effect will be over- 
come. Potassium salts have been found 
to be beneficial, especially in soils poor in 
potash. It has been found in Germany 
that the sugar beet nematode removes 
equally all mineral salts from the roots. 
Therefore to improve such a condition we 
would need to add only that mineral which 
was originally lacking. This may explain 
the effect of potash in combating this dis- 
ease. 

Control of Soil-Infesting Insects. 
Spraying the soil will be of little value in 
the control of underground insect pests. 
Where wire worms are causing injury to 



202 DISEASES OF THE SWEET PEA 

the roots of sweet pea plants, sow corn 
which has been soaked for ten days in water 
containing arsenic or strychnine before the 
sweet pea seeds are planted. The larva 
will attack the poisonous corn kernels and 
die. Another way is to scatter poisoned 
and sweetened corn meal dough which will 
act as a bait. 

White grub, c may be controlled by the 
use of bisulphide of carbon and kerosene 
emulsion. The latter is diluted about ten 
times and poured on the ground about the 
infected plants. This, however, is a risky 
procedure. Fall plowing is a valuable 
remedy since many of the grubs are thus 
exposed to the cold winter weather and 
killed. 

Cut worms may be controlled by the use 
of a poisoned bran made as follows: to 
three ounces of molasses add one gallon 
of water, and sufficient bran to make a 



METHODS OF CONTROL 203 

fairly stiff mixture. To this add Paris 
green or arsenic and stir well into a paste. 
A heaping teaspoonful of the mixture is 
scattered here and there over the infested 
land. 



CHAPTER XI 

SPRAYING 

General Considerations. The or- 
chardist, the nurseryman, the gardener, 
and the florists have already learned the 
necessity of spraying. It often determines 
whether they shall lose a large part of the 
crop or get from it the largest possible 
profit obtainable. It is doubtful if sweet 
pea growers have come to this important 
realization. Many writers on sweet peas 
have in the past attempted to give the im- 
pression that this species is usually free 
from insect and fungous pests. This has 
unfortunately led to an indifference that 
resulted in the quick dissemination of a 

number of dangerous diseases. The streak 

204 



SPRAYING 205 

which is causing so much loss to sweet peas 
in England has gained a strong foothold in 
this country, yet prominent growers and 
seedsmen strenuously deny the existence 
of this disease here. The anthracnose is 
another serious disease, and yet few grow- 
ers have a first hand knowledge of its ex- 
istence. The time is rapidly coming when 
the sweet pea like every other important 
crop will have to be sprayed. The grower 
who fails to do so will be crowded out be- 
cause of competition with others more 
careful. It is true that spraying is no 
pleasant pastime for the grower ; neverthe- 
less, it is a necessary evil, if evil it may be 
called. 

Spraying has two aims : to kill the insect 
and animal pests, and to control fungous 
diseases. The substances which are used 
for the one are without effect on the other. 

Insecticides. All animal and insect 



2o6 DISEASES OF THE SWEET PEA 

pests are best controlled by the use of poi- 
sonous mixtures applied in the form of 
liquid sprays or powders. Insecticides 
may be classified as internal or stomach 
poisons, and external or contact poisons. 
The former kill the biting insects which 
take it into the stomach with the food; the 
latter kill by direct contact, and either 
causes an irritation of the surface of the 
body or clogs the respiratory openings of 
sucking pests. 

(a) Stomach Poisons. Paris green is 
one of the best known of stomach poisons. 
When chemically pure, it is composed of 
copper oxide, acetic acid, and arsenious 
acid. It destroys cutworms, caterpillars, 
beetles, grubs, slugs, etc. On the sweet 
pea it should be applied preferably as a 
liquid, using one pound of the poison and 
one pound of lime to two hundred gallons 
of water. Paris green tends to sink to the 



SPRAYING 207 

bottom of this mixture, and to avoid this 
it must be constantly stirred while being 
applied. This chemical is often adulter- 
ated with white arsenic, causing it to badly 
scorch the treated plants. 

For sweet peas, the use of arsenate of 
lead is to be preferred to Paris green, since 
it is less liable to scorch the foliage, and 
adheres better. Its chemical composition 
consists of acetate of lead and arsenate of 
soda. It is applied to the best advantage 
as a liquid, using about three pounds to 
100 gallons of water. 

Arsenite of zinc may also be used. It is 
a very finely divided fluffy white powder 
which distributes and adheres well to the 
foliage. It is intermediate between Paris 
green and lead arsenate in strength, and 
costs less than either. 

It is essential when arsenicals are used 
to see that they are correctly labeled, and 



208 DISEASES OF THE SWEET PEA 

kept under lock and key as they are poison- 
ous to man and animals. 

Hellebore or white hellebore is some- 
what less dangerous than the arsenicals. 
However, it loses its insecticidal value by 
being exposed to the air. It is a specific 
against slugs in the greenhouse. 

(b) Contact Poisons. All the tobacco 
or nicotine products sold principally as ex- 
tracts or powders belong to this class. A 
common brand much used is the prepara- 
tion known as "Black leaf 40," diluted 1 
part to 700 or 800 of water. An addition 
of soap at the rate of two bars to each 100 
gallons of the solution increases its effec- 
tiveness by making it spread out better. 
Aphine, Sulpho tobacco, and a number of 
other products found on the market are 
usually valuable as contact poisons if prop- 
erly tested out and guaranteed by the 
dealers. 



SPRAYING 209 

Fungicides. These are poisons used to 
control fungous pests. As previously 
stated, some parasitic fungi live on the sur- 
face of the leaves and stems and are there- 
fore easily controlled. An example of this 
is the sweet pea mildew. Other fungi, and 
these are by far in the majority, are those 
which live parasitically in the tissue of the 
host, and therefore cannot be reached. 
Fungicides are only helpful in preventing 
entrance of the parasite in the host. Fun- 
gicides are ineffective in controlling insect 
pests, as are insecticides in controlling 
fungous pests. 

(a) Bordeaux Mixture. This is the 
standard fungicide, especially valuable in 
controlling the sweet pea anthracnose. 
The strength used should be 3 lb. of cop- 
per sulphate, also known as blue stone, 4 
lb. lime, and 50 gallons of water. The 
easiest way to prepare it is to dissolve thor- 



210 DISEASES OF THE SWEET PEA 

oughly the blue stone in 25 gallons of 
water. Use the best quality of lime and 
slake it in a little hot water, being careful, 
however, not to flood it while slaking, nor 
to let it become too dry. When the slak- 
ing is completed, add enough water to 
make 25 gallons. Mix the lime water and 
the blue stone solutions, using first one 
part of lime water, then another part of 
the blue stone. Strain and use at once. 
It is essential that the lime shall not be 
air slaked before it is used. 

The lime water and the blue stone solu- 
tions will keep a long time if they are kept 
in separate receptacles and well covered. 
However, after they are once combined, it 
must be used the same day. Bordeaux 
mixture more than a day old is useless. 
Where Bordeaux is used extensively, stock 
solutions of lime and blue stone should be 
prepared and ready for use. 



SPRAYING 211 

(b) Ammoniacal Copper Carbonate. 
The objection to the use of Bordeaux is 
that it stains the leaves and foliage of the 
sweet pea plant. This is not a serious ob- 
jection when sweet peas are grown for 
seeds or even commercially as a cut flower. 
However, when grown in conservatories 
or in public parks for ornamental purposes, 
the use of Bordeaux becomes objection- 
able. In this case ammoniacal copper car- 
bonate may take the place of Bordeaux, 
since the former is a colorless material. It 
is prepared as follows : 

Copper carbonate 50Z. 

Ammonia (26 Baume') 3 pints 

Water 50 gallons 

This fungicide should be used as soon as 
it is made, as the ammonia evaporates 
quickly. 

(c) Potassium Sulphide. This is a 
valuable fungicide for the control of the 



212 DISEASES OF THE SWEET PEA 

sweet pea mildew. The following strength 
is recommended : 

Potassium sulphide 40Z. 

Water 10 gallons 

(d) Sulphur. Flowers of sulphur are 
often used in greenhouses to control the 
sweet pea mildew. It may be applied 
either by hand or with a duster. 

There are a number of other fungicides 
on the market which are not mentioned. 
They should be thoroughly tested before 
they are used. Considerable discretion 
should be exercised before using a new 
fungicide which claims to be a "cure all." 

Combination Sprays. In the discus- 
sion of the foregoing chapters on fungous 
and insect pests, it is seen that the sweet 
pea is subject to the attacks of more than 
one disease. Spraying, if properly done, 
is effective in controlling or in keeping in 



SPRAYING 213 

check all the pests which attack all the 
parts of the plant above ground. The va- 
rious spray solutions which may or may not 
be combined are indicated by Cooley and 
Swingle * in the following table : 



Tobacco 


Lime 


Bordeaux 


extracts 


sulphur 


mixture 


Paris green yes 


no 


yes 


Arsenate of lead yes 


yes 


yes 


Arsenite of zinc (ortho) yes 


* 


no 


Arsenite of lime yes 


no 


yes 


Lime sulphur yes 


.... 


.... 


Bordeaux yes 


.... 


.... 



* The advisability of making these two combinations 
needs further investigation. 

Each of these preparations is mixed and 
applied just as if it were used alone. A 
combination of the ammoniacal copper 
carbonate with an arsenate would be un- 
safe, since the ammonia renders the arsenic 

1 Cooley, R. A., and Swingle, D. B., A spraying pro- 
gram for Montana orchards. Montana Agr. Expt. Sta- 
tion, Circ. 17: 119-151, 1912. 



214 DISEASES OF THE SWEET PEA 

more soluble, and hence may result in the 
burning of the sweet pea foliage. How- 
ever, it may be mixed to advantage with 
the tobacco products. 

Careful investigations of Professor 
Safro, Entomologist to the Kentucky To- 
bacco Product Co., show that "Black leaf 
40" may be used in combination with such 
spray chemicals as lime sulphur, arsenate 
of lead, arsenite of zinc, and iron sulphate 
for controlling sucking and chewing in- 
sects and fungous diseases, the soap in this 
case being omitted. Professor Safro's 
work further shows that "Black leaf 40" 
may be safely combined with Bordeaux, 
and the desired results obtained. Profes- 
sor Safro writes as follows: "For pur- 
poses of spraying sweet peas, add to every 
100 gallons of Bordeaux three-fourths of 
a pint of 'Black leaf 40/ As far as safety 
to the foliage is concerned, much greater 



SPRAYING 215 

strengths of nicotine may be added to the 
Bordeaux, but no additional effectiveness 
will be given to the mixture as an insecti- 
cide. Any nicotine solution that is used 
for Aphis containing four-hundredths of 
one per cent nicotine will be effective if 
the work is thoroughly done." 

For greenhouse purposes the Auto Spray 
No. 1 is a very desirable spraying machine 
(fig. 43) . It may also be used outdoors on 
small garden lots. In California, where 
large acreages of sweet peas are grown for 
seed, a gasoline sprayer is the proper ma- 
chine. However, as the plants reach three 
to four feet and as the rows begin to touch, 
spraying by power machinery which has to 
be drawn by horses becomes prohibitive. 
In this case two to three Auto Sprays No. 1 
will answer the purpose very well. 



216 DISEASES OF THE SWEET PEA 

PRINCIPLES INVOLVED IN SPRAYING 
SWEET PEAS 

It should be remembered that to destroy 
chewing insects such as caterpillars, etc., 
the stomach poison must be evenly dis- 
tributed all over the plant. This should 
be done as soon as the presence of the pest 
is suspected. Intelligent and observant 
growers will, of course, remember the time 
of appearance of the pest every year, al- 
though the time depends somewhat on the 
climate of each season. In destroying the 
green aphids the contact poison should be 
distributed as evenly as possible on the in- 
sect itself. It is, therefore, best to spray 
for aphids as they are actually found 
working on the plants. With chewing in- 
sects and with fungous pests, however, the 
applications are made even before the par- 
asites appear. Before spraying it is nec- 
essary to have well in mind the organism 



SPRAYING 217 

which is to be destroyed, and the proper 
ingredients used. To keep fungous pests 
in check it is necessary to have the plant 
covered with the fungicide all the time 
infection is feared or suspected. It must 
be remembered that spraying for fungi is 
a form of insurance. It protects the plant 
from becoming infected. However, when 
the parasite penetrates the host, spraying 
is of little value in saving the infected 
plant although it will protect others which 
are as yet healthy. It is essential that the 
sweet pea grower be ever ready to spray 
on time (fig. 46) . Sometimes the retarda- 
tion of even a day may yield negative re- 
sults. The timely destruction of one in- 
sect, or of one spore, undoubtedly means 
the destruction of countless generations of 
these pests. 

Thoroughness is as important in spray- 
ing as it is in everything else in life. Es- 



218 DISEASES OF THE SWEET PEA 

pecially is this true for the control of 
fungous diseases. A spore accidentally 
lodged on a portion of a leaf overlooked 
by the sprayer is like a fortified city 
guarded by rusty cannon. 

Difficulties in the Spraying of 
Sweet Peas. The difficulties in spraying 
sweet peas is that the average fungicide 
will not stick. This is especially true 
where coarse nozzles are used; the liquid 
in this case collects into large drops and 
then rolls off. This difficulty is eliminated 
by the use of very fine nozzles, since the 
finer the spray the greater the success. 
The use of stickers often helps to make 
the spray liquid adhere better to the foli- 
age. With the sweet pea the use of soap 
answers well the purpose of a sticker. 
Add two to three pounds of soap to about 
every 100 gallons of the spray mixture 




*«: 



a> 

■-M o 
■M O 



V 



<v 

xn 

O 



d 
en 






Si 



o 



o 



SPRAYING 219 

used. Where combination sprays are used 
the soap is to be omitted. 

Spraying Greenhouse Sweet Peas. 
Under greenhouse conditions, insect and 
fungous pests are more easily controlled 
than out of doors. In the greenhouse, con- 
ditions are more nearly under the control 
of the grower. By proper cultural care 
many troubles may be kept in check, so that 
spraying may be dispensed with. There 
are, however, certain days when the 
weather is such that proper ventilation is 
difficult if not harmful. The greenhouse 
air then becomes saturated with moisture, 
which favors the development of mildew. 
At other times the house is allowed to get 
too dry and red spiders and aphids make 
their appearance. Theoretically red spi- 
ders and mites may be controlled by fre- 
quent syringings with plain water. Prac- 



220 DISEASES OF THE SWEET PEA 

tically, however, the syringing is not al- 
ways done in the proper way to become 
effective. In this case spraying with a 
standard contact poison becomes necessary. 
Next to red spiders, the only insect that is 
of economic importance is the green aphid. 
Both of these may be kept in check by the 
use of "Black leaf 40," using a dilution of 
one part to one thousand (by volume). 
Aphin or sulpho tobacco may answer the 
same purpose. Some growers prefer the 
use of nico fume tobacco papers. With 
these all that is necessary is to hang the 
paper on any convenient nail and to light 
the end of it. Should mildew appear it 
may be readily controlled by dusting with 
flowers of sulphur, or by spraying with po- 
tassium sulphide, dissolving four ounces 
of the chemical in ten gallons of water. 
The solution should be used at once, as it 
loses its strength by exposure to the air. 



SPRAYING 221 

Outdoor Spraying of Sweet Peas. 
Under our present conditions, it is difficult 
to raise a crop of sweet peas outdoors with- 
out its becoming infested with most of the 
pests enumerated in this book. Spraying 
therefore becomes a necessity. However, 
the grower cannot afford to spray for each 
pest separately. A combination of spray 
mixtures becomes imperative so that one 
application may reach at the root of many 
evils. Red spider, the green aphid, the 
chewing insects, as well as the fungous 
diseases of stems and leaves, may be con- 
trolled by a combination of the following 
materials in the following given propor- 
tions : 

1. Make the regular 5-5-50 Bordeaux 
formula. 

2. If the green aphid is present add to 
every 100 gallons of the Bordeaux three- 
fourths of a pint of "Black leaf 40." 



222 DISEASES OF THE SWEET PEA 

3. To each 100 gallons of 1 and 2, add 
1 lb. of arsenate of lead to keep in check 
the biting insects. If Paris green is used 
instead of arsenate of lead, add one pound 
of extra lime to every pound of the above 
insecticide used. These formulae apply to 
sweet peas grown on large scales. On 
smaller plots, such as the home garden, the 
same formulae hold good except that cal- 
culations are made so that less of the spray 
mixture is prepared at one time. 

With outdoor sweet peas, spraying 
should begin as soon as the plants are six 
inches high and should be continued until 
the plants are about to lose their useful- 
ness. The frequency of the applications 
will depend largely on the weather. The 
more it rains the more often spraying is 
necessary. The object should be to keep 
the plants covered a large part of the grow- 



SPRAYING 223 

ing period with spray materials. Under 
ordinary conditions, spraying every other 
week is a desirable practice. 



INDEX 



INDEX 



Acid phosphate, 182 

Acid soils, 25, 36 

Agrostis neublosa, 58 

Alfalfa, 168, 169 

Alternaria, 178 

Ambrosia sp., 169 

American Sweet Pea So- 
ciety, 6 

Ammonia, 21 1 

Ammoniacal copper car- 
bonate, 211 

Anthracnose, 137, 141, 
157, 176, 181 

Aphids, 142, 155, 157, 158 
161, 163 

Aphine, 208 

Aphelinus, 166 

Aphelinus nigritus, 166 

Aphiduis, 162, 163, 165, 
166 

Aphiduis testaceipes, 162, 
164 

Apple, 139 

Arachnida, 92 

Arsenate of lead, 207 

Arsenate of soda, 207 

Arsenicals, 207 

227 



Arsenate of zinc, 207 
Ascochyta pisi, 151 
Auto Spray No. 1, 215 
Azaleas, 131 

Bacillus lathyri, 144 

Balanced fertilizer, 182 

Beal, A. C, 9, 104 

Beans, 134, 169 

Beets, 169 

Bench, 77 

Bisulphide of carbon, 180 

Blackberry, wild, 134 

Black blister beetle, 169 

Black leaf 40, 208, 214 

Black leaf 40 and lime sul- 
phur, 214 

Black leaf 40 and arsenate 
of lead, 214 

Black leaf 40 and arsenate 
of zinc, 214 

Black leaf 40 and iron 
sulphate, 214 

Black leaf 40 and Bor- 
deaux, 214 

Blister beetles, 168 

Blue stone, 209 



228 



INDEX 



Bordeaux mixture, 209, 

219 
Botrytis, 178 
Bud drop, 181 

Camel's hair brush, 70 
Carnation, 89 
Caterpillars, 170 
Chaetomium root rot, 104- 

109 
Chaetomium spirochaete, 

104 
Cheesecloth, 54 
Chrysopa californica, 161 
Chittenden, F. J., 112, 113, 

152, 170 
Christmas trade, 79 
Chrysanthemums, 89 
Clover, 168, 169 
Cleanliness, 198 
Climate, 63 
Clonostachys, 178 
Clump method, 34, 45 
Cole, 12 

Collar rot, 97, 119, 123 
Combination sprays, 212, 

213 
Contact poisons, 208 
Control of sick soils, 190, 

197 
Cooley, R. A., 213 
Copper carbonate, 211 
Copper sulphate, 209 
Cordon system, 36 



Corn, 128, 169 

Corticium vagum, 98 

Cotton, 168 

Cow pea, 115, 134 

Crab grass, 128 

Crop rotation, 199 

Croton, 131 

Cucumber, 122 

Cultivation, 48 

Cultural considerations, 

196 
Culture under glass, 74 
Cupid sweet peas, 11, 12 
Cuthbertson, F. G., 38 
Cut worms, 202 

Dahlia, 131, 134 
Damping off, 95, 96 
DeBary, 3 
Diabrotica 12 punctata, 

167 
Diseased seed, 176 
Dispodding, 49 
Downy mildew of grapes, 

4 
Drug store beetle, 178 

Early flowering, 21 
Eckford, Henry, 11, 12, 14, 

46 
Eel worm, 123 
Empusa aphidis, 166, 167 
Epicauta Pennsylvanica, 

169 



INDEX 



229 



Epicauta vittata, 169 
Erisiphe polygoni, 118 
Evaporation, 94 
Exhibiting, 54, 55 

Fall planting, 27, 28 
Ferns, 131 
Fertilizers, 76, 181 
Field diseases, 135 
Flail, 69 

Flower pathology, 5 
Formaldehyde, 189, 194 
Fungicides, 209 
Fusarium, 178 
Fusarium lathyri, 109 
Fusarium root rot, 109- 
112 

Geranium, wild, 134 
Glomerella rufomaculans, 

137» 181 
Grasshopper, 170 
Green lace wing, 161 
Grubs, 174 
Gysophila, 58 

Hard wood ashes, 184 
Harris, J. E., 98 
Heliothrips hsemorrhoi- 

dalis, 129 
Hellebore, 208 
Heterodera radicicola, 123 
Hippodamia convergens 

158 



History of the sweet pea, 

9 

Hollyhock diseases, 6 
Honey flies, 161 
Hutchins, 26 

Infected areas, 196 
Infected manure, 196 
Insect pests, 152, 171 
Insecticides, 205 
Introduction, 1 
Irrigation, 72, 73 

Jamestown weed, 134 
Johnson grass, 128 
Judging, 72 

Kentucky Product Co., 214 
Kerr, G. W., 57 
Kew Bulletin, 113 

Labeling, 35 
Lady beetles, 158 
Lachnosterna, 174 
Lathyrus odoratus, 10 
Lathyrus species, 27 
Lettuce, 122 
Light, 97 
Lilies, 131 
Lime, 98, 209 
Lime water, 210 
Lime application, 25 
Litmus paper, 98 

Macrosiphum pisi, 152 



230 



INDEX 



Maggots, 160, 161 
Mangels, 169 
Manns, T. F., 144 
Manure, 86, 199 
Manure mulch, 28, 29 
Marketing, 51 
Market varieties, 22 
Massee, G., 113, 118, 149 

151 
May beetle, 174 
Melanotus communis, 173 
Melons, 169 
Mendelian principle, 69 
Metamorphosis, 92 
Methods of control, 185 
Microsphera alni, 118 
Millardet, M., 4 
Mites, 92 
Moisture, 93, 94 
Morse, C. C, 38, 60 
Mosaic, 141-144 
Mulching, 49 
Muriate of potash, 182 

Nematode galls, 123 
Netting, 43, 44, 46, 47 
Nicotine, 215 
Nozzles, 218 

Orchid flowering, 78, 84 

Packing, 53, 56 
Paper boxes, 53 
Paris green, 206, 207 



Parsnip, 115 
Parthenogenesis, 156 
Patterson, Flora, Mrs., 105 
Pea blight, 149-150 
Pea spot, 151 
Peach yellows, 143 
Perennial rye grass, 128 
Peridroma saucia, 171 
Peronospora trifoliorum, 

149, 151 
Peronospora vicise, 150 
Philips, W. J., 165 
Phlox, 131 
Physiological diseases, 181- 

184 
Picking, 51, 52, 86 
Pink, 131 
Planting, 25, 31 
Pollination, 69, 70 
Potato, 169 

Potato blight, epidemic, 2 
Potassuim sulphide, 211 
Powdery mildew, 118, 119 
Preparation, 23, 27 

Radish, 169 

Rag weed, 169 

Red shell soil, 75 

Red spider, 92, 131-134, 

142-145 
Red top, 128 
Resistant varieties, 186 
Rhizoctonia root rot, 98- 

104 



INDEX 



231 



Rhizopus, 178 
Rogueing, 66, 67 
Rolfs, F. M., 103 
Root burn, 182 
Root knot, 123-129 
Rye, 128, 168 

Sackett, W. G., 99 

Safro, Prof., 214 

Sclerotinia libertiana, 119 

Scorch or scald, 54 

Sclerotia, 122 

Seed, 25 

Seed treatment, 35, 82, 188 

Selby, A. D., 99 

Selection, 66, 67 

Shading, 54 

Shamel, A. D., 193 

Shaw, J. F. J., 103 

Shriveled seed, 177 

Site, 22 

Sitodrepa panicea, 178 

Slow germination, 26 

Soap, 218 

Soil acidity, 98 

Soil insects, 17 1 

Solid beds, 76 

Sowing, 34, 35 

Sowing in pots, 34 

Spencer varieties, 15, 61, 

62, 67 
Spraying, 204 
Spraying formula, 221, 

222 



Spring planting, 29 
Stackman, E. C, 99 
Steam sterilization, 191 
Stewart, F. C, 118 
Stickers, 218 
Stomach poisons, 206 
Streak, 7, 113, 157, 176 
String, 44, 45, 85 
Striped blister beetle, 169 
Sulpho tobacco, 208 
Sulphur, 212 
Supports, 36, 37, 38, 40, 

41, 42, 44, 45, 46, 66, 

88 
Sweat flies, 161 
Sweet Pea Annual, 39, 

112, 118, 149 
Swingle, D. B., 213 
Syrphid fly, 158, 160 
Syrphus ribesii, 160 

Taubenhaus, J. J., 141 
Temperature, 83, 84, 88, 

93. 96 

Tetranchys bimaculatus, 

131 

Thielavia basicola, 112 
Thielavia root rot, 98, 1 12- 

117 
Thinning, 33 
Thrips, 129-131 
Tillage, 48 
Timothy, 128 
Tobacco, 115, 168 



232 



INDEX 



Tomato, 87, 88, 122, 133, 

134 

Transpiration, 94, 95 

Trench method, 32 
Trial ground, 71 
Triphleps insidiosus, 133, 

134 
Turnip, 169 

Twelve spotted cucumber 
beetle, 167 

Variegated cutworms, 171 

Varieties, 10, 12, 13, 14, 

15, 16, 17, 18, 19, 20, 

21, 22, 54, 5$, 58, 78, 

79 
Vases, 52, 57, 59 



Ventilation, 36 
Verbena, 131 

Violets, 88, 89, 115, 122, 
133. 134 

Watering, 36, 37, 48, 49, 

81, 93, 94, 95 
Wax paper, 53 
Webster, F. M., 165 
White grubs, 174, 202 
White hellebore, 208 
Wind currents, 93 
Wire, 85 
Wireworms, 173, 174 

Zinnia, 128 

Zvolanek, A. C, 74, 78 



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